diff --git a/workers/main/src/activities/weeklyFinancialReports/index.ts b/workers/main/src/activities/weeklyFinancialReports/index.ts
index 8a800f7..7ba3212 100644
--- a/workers/main/src/activities/weeklyFinancialReports/index.ts
+++ b/workers/main/src/activities/weeklyFinancialReports/index.ts
@@ -1,2 +1,3 @@
 export * from './fetchFinancialAppData';
 export * from './getTargetUnits';
+export * from './sendReportToSlack';
diff --git a/workers/main/src/activities/weeklyFinancialReports/sendReportToSlack.test.ts b/workers/main/src/activities/weeklyFinancialReports/sendReportToSlack.test.ts
new file mode 100644
index 0000000..2b02cad
--- /dev/null
+++ b/workers/main/src/activities/weeklyFinancialReports/sendReportToSlack.test.ts
@@ -0,0 +1,141 @@
+import { beforeEach, describe, expect, it, Mock, vi } from 'vitest';
+
+import { AppError } from '../../common/errors';
+import { readJsonFile } from '../../common/fileUtils';
+import { TargetUnit } from '../../common/types';
+import { FinancialsAppData } from '../../services/FinApp';
+import { SlackService } from '../../services/SlackService';
+import { WeeklyFinancialReportRepository } from '../../services/WeeklyFinancialReport';
+import { sendReportToSlack } from './sendReportToSlack';
+
+vi.mock('../../common/fileUtils', () => ({
+  readJsonFile: vi.fn(),
+}));
+vi.mock('../../services/WeeklyFinancialReport', () => ({
+  WeeklyFinancialReportRepository: vi.fn(),
+}));
+vi.mock('../../services/SlackService', () => ({
+  SlackService: vi.fn(),
+}));
+
+const mockTargetUnits: TargetUnit[] = [
+  {
+    group_id: 1,
+    group_name: 'Group',
+    project_id: 2,
+    project_name: 'Project',
+    user_id: 3,
+    username: 'User',
+    spent_on: '2024-06-01',
+    total_hours: 8,
+  },
+];
+const mockFinancialsAppData: FinancialsAppData = {
+  employees: [{ redmine_id: 3, history: { rate: { '2024-06-01': 100 } } }],
+  projects: [{ redmine_id: 2, history: { rate: { '2024-06-01': 200 } } }],
+};
+
+describe('sendReportToSlack', () => {
+  let readJsonFileMock: Mock;
+  let generateReportMock: Mock;
+  let postMessageMock: Mock;
+
+  function tryMockReset(obj: unknown) {
+    if (
+      typeof obj === 'function' &&
+      'mockReset' in obj &&
+      typeof (obj as { mockReset: unknown }).mockReset === 'function'
+    ) {
+      (obj as { mockReset: () => void }).mockReset();
+    }
+  }
+
+  beforeEach(() => {
+    readJsonFileMock = vi.mocked(readJsonFile);
+    generateReportMock = vi.fn();
+    postMessageMock = vi.fn();
+
+    tryMockReset(WeeklyFinancialReportRepository);
+    tryMockReset(SlackService);
+  });
+
+  it('sends report to Slack and returns success message', async () => {
+    readJsonFileMock
+      .mockResolvedValueOnce(mockTargetUnits)
+      .mockResolvedValueOnce(mockFinancialsAppData);
+    generateReportMock.mockReturnValue({
+      details: 'details',
+      summary: 'summary',
+    });
+    (WeeklyFinancialReportRepository as unknown as Mock).mockImplementation(
+      () => ({
+        generateReport: generateReportMock,
+      }),
+    );
+    postMessageMock
+      .mockResolvedValueOnce({ ts: '123' })
+      .mockResolvedValueOnce({});
+    (SlackService as unknown as Mock).mockImplementation(() => ({
+      postMessage: postMessageMock,
+    }));
+
+    const result = await sendReportToSlack('target.json', 'finapp.json');
+
+    expect(result).toBe('Report sent to Slack');
+    expect(readJsonFileMock).toHaveBeenCalledTimes(2);
+    expect(generateReportMock).toHaveBeenCalled();
+    expect(postMessageMock).toHaveBeenCalledTimes(2);
+    expect(postMessageMock).toHaveBeenCalledWith('summary');
+    expect(postMessageMock).toHaveBeenCalledWith('details', '123');
+  });
+
+  it('throws AppError if readJsonFile fails', async () => {
+    readJsonFileMock.mockRejectedValueOnce(new Error('fail'));
+    await expect(
+      sendReportToSlack('target.json', 'finapp.json'),
+    ).rejects.toThrow(AppError);
+    await expect(
+      sendReportToSlack('target.json', 'finapp.json'),
+    ).rejects.toThrow('Failed to send report to Slack');
+  });
+
+  it('throws AppError if generateReport fails', async () => {
+    readJsonFileMock
+      .mockResolvedValueOnce(mockTargetUnits)
+      .mockResolvedValueOnce(mockFinancialsAppData);
+    generateReportMock.mockRejectedValueOnce(new Error('fail-gen'));
+    (WeeklyFinancialReportRepository as unknown as Mock).mockImplementation(
+      () => ({
+        generateReport: generateReportMock,
+      }),
+    );
+    (SlackService as unknown as Mock).mockImplementation(() => ({
+      postMessage: postMessageMock,
+    }));
+    await expect(
+      sendReportToSlack('target.json', 'finapp.json'),
+    ).rejects.toThrow(AppError);
+  });
+
+  it('throws AppError if postMessage fails', async () => {
+    readJsonFileMock
+      .mockResolvedValueOnce(mockTargetUnits)
+      .mockResolvedValueOnce(mockFinancialsAppData);
+    generateReportMock.mockReturnValue({
+      details: 'details',
+      summary: 'summary',
+    });
+    (WeeklyFinancialReportRepository as unknown as Mock).mockImplementation(
+      () => ({
+        generateReport: generateReportMock,
+      }),
+    );
+    postMessageMock.mockRejectedValueOnce(new Error('fail-post'));
+    (SlackService as unknown as Mock).mockImplementation(() => ({
+      postMessage: postMessageMock,
+    }));
+    await expect(
+      sendReportToSlack('target.json', 'finapp.json'),
+    ).rejects.toThrow(AppError);
+  });
+});
diff --git a/workers/main/src/activities/weeklyFinancialReports/sendReportToSlack.ts b/workers/main/src/activities/weeklyFinancialReports/sendReportToSlack.ts
new file mode 100644
index 0000000..e889186
--- /dev/null
+++ b/workers/main/src/activities/weeklyFinancialReports/sendReportToSlack.ts
@@ -0,0 +1,36 @@
+import { AppError } from '../../common/errors';
+import { readJsonFile } from '../../common/fileUtils';
+import { TargetUnit } from '../../common/types';
+import { FinancialsAppData } from '../../services/FinApp';
+import { SlackService } from '../../services/SlackService';
+import { WeeklyFinancialReportRepository } from '../../services/WeeklyFinancialReport';
+
+export const sendReportToSlack = async (
+  targetUnitsFileLink: string,
+  financialAppDataFileLink: string,
+): Promise<string> => {
+  try {
+    const [targetUnits, { employees, projects }] = await Promise.all([
+      readJsonFile<TargetUnit[]>(targetUnitsFileLink),
+      readJsonFile<FinancialsAppData>(financialAppDataFileLink),
+    ]);
+    const weeklyFinancialReportRepository =
+      new WeeklyFinancialReportRepository();
+    const { details, summary } =
+      await weeklyFinancialReportRepository.generateReport({
+        targetUnits,
+        employees,
+        projects,
+      });
+    const slackService = new SlackService();
+    const message = await slackService.postMessage(summary);
+
+    await slackService.postMessage(details, message.ts);
+
+    return 'Report sent to Slack';
+  } catch (err) {
+    const message = err instanceof Error ? err.message : String(err);
+
+    throw new AppError('Failed to send report to Slack', message);
+  }
+};
diff --git a/workers/main/src/services/FinApp/types.ts b/workers/main/src/services/FinApp/types.ts
index 67021a1..b37ee10 100644
--- a/workers/main/src/services/FinApp/types.ts
+++ b/workers/main/src/services/FinApp/types.ts
@@ -23,3 +23,8 @@ export interface Project {
   history?: History;
   [key: string]: unknown;
 }
+
+export interface FinancialsAppData {
+  projects: Project[];
+  employees: Employee[];
+}