diff --git a/app/controllers/mm/users_controller.rb b/app/controllers/mm/users_controller.rb
index 875ca724..793a9ff1 100644
--- a/app/controllers/mm/users_controller.rb
+++ b/app/controllers/mm/users_controller.rb
@@ -1,7 +1,7 @@
 class Mm::UsersController < Base::HyaccController
 
   def index
-    @users = User.paginate page: params[:page], per_page: current_user.slips_per_page
+    @users = User.includes(:employee).paginate page: params[:page], per_page: current_user.slips_per_page
   end
 
   def show
@@ -43,16 +43,50 @@ def update
     begin
       @user.transaction do
         @user.update!(user_params)
-      
-        flash[:notice] = 'ユーザを更新しました。'
-        render 'common/reload'
       end
+
+      flash[:notice] = 'ユーザを更新しました。'
+      render 'common/reload'
     rescue => e
       handle(e)
       render :edit
     end
   end
 
+  def grant_admin
+    @user = User.find(params[:id])
+    begin
+      @user.transaction do
+        @user.update!(admin: true)
+      end
+
+      flash[:notice] = '管理権限を付与しました。'
+      redirect_after_admin_change
+    rescue => e
+      handle(e)
+      redirect_after_admin_change
+    end
+  end
+
+  def revoke_admin
+    @user = User.find(params[:id])
+    begin
+      @user.transaction do
+        @user.update!(admin: false)
+      end
+
+      flash[:notice] = '管理権限を解除しました。'
+      if current_user.id == @user.id
+        redirect_to root_path
+      else
+        redirect_after_admin_change
+      end
+    rescue => e
+      handle(e)
+      redirect_after_admin_change
+    end
+  end
+
   def destroy
     id = params[:id].to_i
     user = User.find(id)
@@ -93,6 +127,7 @@ def user_params
         :zip_code, :address, :sex, :business_office_id, :birth, :my_number
       ]
     ]
+    permitted << :admin if action_name == 'create'
 
     ret = params.require(:user).permit(permitted)
 
@@ -103,7 +138,7 @@ def user_params
     ret
   end
 
-  def employee_params   
+  def employee_params
     return {} unless params.dig(:employee)
     permitted = [
       branch_employees_attributes: [
@@ -111,4 +146,13 @@ def employee_params
     ]
     params.require(:employee).permit(permitted)
   end
-end
\ No newline at end of file
+
+  def redirect_after_admin_change
+    if current_company.personal?
+      redirect_to action: 'index'
+    else
+      redirect_to mm_employees_path
+    end
+  end
+end
+
diff --git a/app/models/employee.rb b/app/models/employee.rb
index a111da94..2c535d0e 100644
--- a/app/models/employee.rb
+++ b/app/models/employee.rb
@@ -72,6 +72,10 @@ def disabled_name
     DISABLED_TYPES[disabled]
   end
 
+  def user_loginable?
+    user.present? && user.loginable?(self)
+  end
+
   def fullname(separetor = ' ')
     "#{last_name}#{separetor}#{first_name}"
   end
diff --git a/app/models/employee_finder.rb b/app/models/employee_finder.rb
index aaaeed8c..fc69ca35 100644
--- a/app/models/employee_finder.rb
+++ b/app/models/employee_finder.rb
@@ -10,7 +10,9 @@ def disabled_types
   end
 
   def list
-    Employee.where(conditions).paginate(page: page, per_page: per_page)
+    Employee.where(conditions)
+      .includes(:user)
+      .paginate(page: page, per_page: per_page)
   end
 
   private
diff --git a/app/models/user.rb b/app/models/user.rb
index a0086c05..cfed8c8d 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -24,14 +24,22 @@ class User < ApplicationRecord
     )
   }
 
+  def loginable?(employee_record = nil)
+    emp = employee_record || employee
+    !deleted? && !emp.disabled? && !emp.deleted?
+  end
+
   def active_admin?
-    admin? && !deleted? && !employee.disabled? && !employee.deleted?
+    admin? && loginable?
   end
 
   def would_remove_last_active_admin?
-    return false unless admin?
-    return false if deleted_in_database
-    return false if employee.deleted_in_database || employee.disabled_in_database
+    was_active = admin_in_database && !deleted_in_database &&
+      !employee.deleted_in_database && !employee.disabled_in_database
+    return false unless was_active
+
+    will_be_active = admin? && !deleted? && !employee.disabled? && !employee.deleted?
+    return false if will_be_active
 
     company_active_admins = self.class.active_admins.where(employees: { company_id: employee.company_id })
     company_active_admins.where.not(id: id).none?
diff --git a/app/models/validators/last_active_admin_validator.rb b/app/models/validators/last_active_admin_validator.rb
index 59ab6faf..26225285 100644
--- a/app/models/validators/last_active_admin_validator.rb
+++ b/app/models/validators/last_active_admin_validator.rb
@@ -17,10 +17,17 @@ def validate(record)
     private
 
     def validate_user(user)
-      return unless user.will_save_change_to_deleted? && user.deleted?
+      becoming_inactive = (user.will_save_change_to_deleted? && user.deleted?) ||
+                          (user.will_save_change_to_admin? && !user.admin?)
+      return unless becoming_inactive
       return unless user.would_remove_last_active_admin?
 
-      user.errors.add(:base, HyaccErrors::ERR_LAST_ACTIVE_ADMIN_DELETE)
+      error = if user.will_save_change_to_admin? && !user.admin?
+                HyaccErrors::ERR_LAST_ACTIVE_ADMIN_REVOKE
+              else
+                HyaccErrors::ERR_LAST_ACTIVE_ADMIN_DELETE
+              end
+      user.errors.add(:base, error)
     end
 
     def validate_employee(employee)
diff --git a/app/utils/hyacc_errors.rb b/app/utils/hyacc_errors.rb
index 148415f7..7cd52a03 100644
--- a/app/utils/hyacc_errors.rb
+++ b/app/utils/hyacc_errors.rb
@@ -30,6 +30,7 @@ module HyaccErrors
   ERR_ILLEGAL_TAX_DETAIL = "消費税は税抜経理方式の場合のみ指定可能です。"
   ERR_LAST_ACTIVE_ADMIN_DELETE = "ログイン可能な管理権限を持つユーザーが0人になるため、削除できません。"
   ERR_LAST_ACTIVE_ADMIN_DISABLE = "ログイン可能な管理権限を持つユーザーが0人になるため、無効にできません。"
+  ERR_LAST_ACTIVE_ADMIN_REVOKE = "ログイン可能な管理権限を持つユーザーが0人になるため、管理権限を解除できません。"
   ERR_NO_CAPITATION_TARGET_BRANCH_EXISTS = "人頭割で配賦できる部門がありません。"
   ERR_NOT_JOURNALIZABLE_ACCOUNT = "仕訳が登録できない勘定科目が指定されています。"
   ERR_OVERRIDE_NEEDED = "サブクラスでの実装が必要です。"
diff --git a/app/views/mm/employees/index.html.erb b/app/views/mm/employees/index.html.erb
index b8d5b97c..0de6157c 100644
--- a/app/views/mm/employees/index.html.erb
+++ b/app/views/mm/employees/index.html.erb
@@ -11,6 +11,7 @@
         <th class="text-center"><%= Employee.human_attribute_name :social_insurance_birthday %></th>
         <th class="text-center">業務経歴</th>
         <th class="text-center">状態</th>
+        <th class="text-center"><%= User.human_attribute_name :admin %></th>
         <th></th>
       </tr>
     </thead>
@@ -30,6 +31,13 @@
           </td>
           <td class="text-center"><%= e.disabled_name %></td>
           <td class="text-center">
+            <% if e.user_loginable? %>
+              <%= e.user.admin? ? 'あり' : 'なし' %>
+            <% else %>
+              -
+            <% end %>
+          </td>
+          <td class="text-center text-nowrap">
             <%= link_to '編集', edit_mm_employee_path(e), remote: true, class: 'btn btn-sm btn-light' %>
             <% if e.disabled? %>
               <%= link_to '削除', mm_employee_path(e), data: {confirm: '削除します。よろしいですか？'}, method: 'delete', class: 'btn btn-sm btn-danger' %>
diff --git a/app/views/mm/employees/show.js.erb b/app/views/mm/employees/show.js.erb
index 7e943a63..95ac2bda 100644
--- a/app/views/mm/employees/show.js.erb
+++ b/app/views/mm/employees/show.js.erb
@@ -15,4 +15,36 @@ options.buttons.push(
   }
 );
 
-hyacc.current_dialog(options).show('<%=j render 'show' %>');
\ No newline at end of file
+<% if @e.user_loginable? %>
+  <% if @e.user.admin? %>
+    options.buttons.push({
+      text: '管理権限を解除',
+      class: 'btn btn-light',
+      click: function() {
+        if (confirm('管理権限を解除します。よろしいですか？')) {
+          hyacc.current_dialog().close();
+          var form = $('<form>', { method: 'post', action: '<%= revoke_admin_mm_user_path(@e.user) %>' });
+          form.append($('<input>', { type: 'hidden', name: 'authenticity_token', value: '<%= form_authenticity_token %>' }));
+          $('body').append(form);
+          form.submit();
+        }
+      }
+    });
+  <% else %>
+    options.buttons.push({
+      text: '管理権限を付与',
+      class: 'btn btn-light',
+      click: function() {
+        if (confirm('管理権限を付与します。よろしいですか？')) {
+          hyacc.current_dialog().close();
+          var form = $('<form>', { method: 'post', action: '<%= grant_admin_mm_user_path(@e.user) %>' });
+          form.append($('<input>', { type: 'hidden', name: 'authenticity_token', value: '<%= form_authenticity_token %>' }));
+          $('body').append(form);
+          form.submit();
+        }
+      }
+    });
+  <% end %>
+<% end %>
+
+hyacc.current_dialog(options).show('<%=j render 'show' %>');
diff --git a/app/views/mm/users/_form.html.erb b/app/views/mm/users/_form.html.erb
index 79911462..754a106a 100644
--- a/app/views/mm/users/_form.html.erb
+++ b/app/views/mm/users/_form.html.erb
@@ -28,6 +28,10 @@
           <th><%= f.label :password %></th>
           <td><%= f.password_field :password, autocomplete: "new-password", class: 'form-control form-control-sm' %></td>
         </tr>
+        <tr>
+          <th><%= f.label :admin %></th>
+          <td><%= f.check_box :admin, class: 'form-check-input' %></td>
+        </tr>
       <% end %>
 
       <%= f.fields_for "employee_attributes", @user.employee do |f| %>
diff --git a/app/views/mm/users/index.html.erb b/app/views/mm/users/index.html.erb
index e41f5eb1..b93cda8f 100644
--- a/app/views/mm/users/index.html.erb
+++ b/app/views/mm/users/index.html.erb
@@ -6,6 +6,7 @@
       <tr>
         <th class="text-center"><%= User.human_attribute_name :login_id %></th>
         <th>氏名</th>
+        <th class="text-center"><%= User.human_attribute_name :admin %></th>
         <th class="text-center">状態</th>
         <th class="text-center"></th>
       </tr>
@@ -15,6 +16,13 @@
         <tr>
           <td class="text-center"><%= user.login_id %></td>
           <td><%= link_to user.employee.fullname, {action: 'show', id: user.id}, class: 'show', remote: true %></td>
+          <td class="text-center">
+            <% if user.loginable? %>
+              <%= user.admin? ? 'あり' : 'なし' %>
+            <% else %>
+              -
+            <% end %>
+          </td>
           <td class="text-center"><%= HyaccConst::DELETED_TYPES[user.deleted] %></td>
           <td class="text-center text-nowrap">
             <%= link_to '編集', {action: 'edit', id: user.id}, remote: true, class: 'btn btn-sm btn-light' %>
diff --git a/app/views/mm/users/show.js.erb b/app/views/mm/users/show.js.erb
new file mode 100644
index 00000000..11fc9133
--- /dev/null
+++ b/app/views/mm/users/show.js.erb
@@ -0,0 +1,39 @@
+var options = {
+  title: '<%= title.present? ? title + '　参照' : '参照' %>'
+};
+
+options.buttons = [];
+
+<% if @user.loginable? %>
+  <% if @user.admin? %>
+    options.buttons.push({
+      text: '管理権限を解除',
+      class: 'btn btn-light',
+      click: function() {
+        if (confirm('管理権限を解除します。よろしいですか？')) {
+          hyacc.current_dialog().close();
+          var form = $('<form>', { method: 'post', action: '<%= revoke_admin_mm_user_path(@user) %>' });
+          form.append($('<input>', { type: 'hidden', name: 'authenticity_token', value: '<%= form_authenticity_token %>' }));
+          $('body').append(form);
+          form.submit();
+        }
+      }
+    });
+  <% else %>
+    options.buttons.push({
+      text: '管理権限を付与',
+      class: 'btn btn-light',
+      click: function() {
+        if (confirm('管理権限を付与します。よろしいですか？')) {
+          hyacc.current_dialog().close();
+          var form = $('<form>', { method: 'post', action: '<%= grant_admin_mm_user_path(@user) %>' });
+          form.append($('<input>', { type: 'hidden', name: 'authenticity_token', value: '<%= form_authenticity_token %>' }));
+          $('body').append(form);
+          form.submit();
+        }
+      }
+    });
+  <% end %>
+<% end %>
+
+hyacc.current_dialog(options).show('<%=j render 'show' %>');
diff --git a/config/locales/hyacc.ja.yml b/config/locales/hyacc.ja.yml
index 479b031f..d59821ef 100644
--- a/config/locales/hyacc.ja.yml
+++ b/config/locales/hyacc.ja.yml
@@ -281,6 +281,7 @@ ja:
 
       user:
         account_count_of_frequencies: 勘定科目の優先表示数
+        admin: 管理権限
         code: "コード"
         password: パスワード
         first_name: "名前"
diff --git a/config/routes/mm.rb b/config/routes/mm.rb
index c2d4ff59..fd86f3ea 100644
--- a/config/routes/mm.rb
+++ b/config/routes/mm.rb
@@ -66,6 +66,10 @@
       collection do
         get 'add_branch'
       end
+      member do
+        post 'grant_admin'
+        post 'revoke_admin'
+      end
     end
   end
 end
diff --git a/test/controllers/mm/users_controller_test.rb b/test/controllers/mm/users_controller_test.rb
index 2a2f5385..59e8d886 100644
--- a/test/controllers/mm/users_controller_test.rb
+++ b/test/controllers/mm/users_controller_test.rb
@@ -43,8 +43,9 @@ def test_create_with_valid_branch_employees_params
  
     assert_response :success
     
-    u = User.find_by_login_id('zero')
+    u = assigns(:user)
     assert_not_nil u
+    assert_not u.admin?
     assert_not_nil u.employee
     assert_equal 'test_create', u.employee.last_name
     assert_equal 'a', u.employee.first_name
@@ -54,6 +55,60 @@ def test_create_with_valid_branch_employees_params
     assert_equal 2, u.employee.default_branch.id
   end
 
+  def test_createでadminを付与できる
+    sign_in admin
+
+    params = user_params_with_valid_branch_employees
+    params[:user][:admin] = true
+
+    post :create, xhr: true, params: params
+
+    assert_response :success
+    assert assigns(:user).admin?
+  end
+
+  def test_grant_admin
+    sign_in admin
+
+    post :grant_admin, params: {id: user.id}
+
+    assert_redirected_to mm_employees_path
+    assert user.reload.admin?
+  end
+
+  def test_revoke_admin
+    other_admin = User.find(6)
+    other_admin.update!(admin: true)
+
+    sign_in admin
+    post :revoke_admin, params: {id: other_admin.id}
+
+    assert_redirected_to mm_employees_path
+    assert_not other_admin.reload.admin?
+  end
+
+  def test_ログイン可能な管理権限を持つユーザーが1人のとき_adminを解除できない
+    sign_in admin
+
+    post :revoke_admin, params: {id: admin.id}
+
+    assert_redirected_to mm_employees_path
+    assert admin.reload.admin?
+    assert flash[:is_error_message]
+    assert_equal ERR_LAST_ACTIVE_ADMIN_REVOKE, flash[:notice]
+  end
+
+  def test_ログイン可能な管理権限を持つユーザーが2人のとき_自分自身のadminを解除できる
+    other_admin = User.find(6)
+    other_admin.update!(admin: true)
+
+    sign_in admin
+    post :revoke_admin, params: {id: admin.id}
+
+    assert_redirected_to root_path
+    assert_not admin.reload.admin?
+  end
+
   def test_create_with_invalid_branch_employees_params
     sign_in admin
 
diff --git a/test/models/employee_test.rb b/test/models/employee_test.rb
index 4bfaeda1..1793c1f9 100644
--- a/test/models/employee_test.rb
+++ b/test/models/employee_test.rb
@@ -24,4 +24,20 @@ def test_representative_or_family_type_name
     assert_nil Employee.find(1).representative_or_family_type_name
   end
 
+  def test_user_loginable_ユーザなしはfalse
+    e = Employee.new
+    assert_not e.user_loginable?
+  end
+
+  def test_user_loginable_ログイン可能なユーザがいればtrue
+    e = user.employee
+    assert e.user_loginable?
+    assert e.user.loginable?(e)
+  end
+
+  def test_user_loginable_無効化済み従業員はfalse
+    e = users(:disabled_employee_user).employee
+    assert_not e.user_loginable?
+  end
+
 end
diff --git a/test/models/user_test.rb b/test/models/user_test.rb
index 36d75be3..9b829373 100644
--- a/test/models/user_test.rb
+++ b/test/models/user_test.rb
@@ -35,6 +35,20 @@ def test_削除済み従業員に紐づくユーザはログイン不可
     assert_not users(:deleted_employee_user).active_for_authentication?
   end
 
+  def test_loginable_削除済みユーザはfalse
+    assert_not users(:deleted_user).loginable?
+  end
+
+  def test_loginable_無効化済み従業員に紐づくユーザはfalse
+    assert_not users(:disabled_employee_user).loginable?
+  end
+
+  def test_active_admin_無効化済みユーザでadminフラグがtrueでもfalse
+    u = users(:disabled_employee_user)
+    u.admin = true
+    assert_not u.active_admin?
+  end
+
   def test_would_remove_last_active_admin_非adminはfalse
     assert_not user.admin?
     assert_not user.would_remove_last_active_admin?
diff --git a/test/models/validators/last_active_admin_validator_test.rb b/test/models/validators/last_active_admin_validator_test.rb
index 875a607b..d9ba54bc 100644
--- a/test/models/validators/last_active_admin_validator_test.rb
+++ b/test/models/validators/last_active_admin_validator_test.rb
@@ -79,4 +79,24 @@ def test_ログイン可能な管理権限を持つユーザーが2人のとき_
     assert other_admin.employee.valid?
   end
 
+  def test_ログイン可能な管理権限を持つユーザーが1人のとき_adminを解除できない
+    assert admin.admin?
+    assert admin.active_admin?
+
+    admin.admin = false
+    assert admin.invalid?
+    assert_equal ERR_LAST_ACTIVE_ADMIN_REVOKE, admin.errors[:base].first
+  end
+
+  def test_ログイン可能な管理権限を持つユーザーが2人のとき_adminを解除できる
+    other_admin = User.find(6)
+
+    other_admin.update!(admin: true)
+    assert admin.admin?
+    assert other_admin.admin?
+
+    admin.admin = false
+    assert admin.valid?
+  end
+
 end