diff --git a/dictation_server/src/features/users/test/users.service.mock.ts b/dictation_server/src/features/users/test/users.service.mock.ts
index 803014e..53c590a 100644
--- a/dictation_server/src/features/users/test/users.service.mock.ts
+++ b/dictation_server/src/features/users/test/users.service.mock.ts
@@ -21,6 +21,7 @@ export type UsersRepositoryMockValue = {
   createNormalUser: User | Error;
   findSameAccountUsers: User[] | Error;
   findUserByExternalId: User | Error;
+  existsAuthorId: boolean | Error;
 };
 
 export type AdB2cMockValue = {
@@ -188,6 +189,7 @@ export const makeUsersRepositoryMock = (value: UsersRepositoryMockValue) => {
     createNormalUser,
     findSameAccountUsers,
     findUserByExternalId,
+    existsAuthorId,
   } = value;
 
   const aIdError = new authorIdError('ER_DUP_ENTRY');
@@ -219,6 +221,10 @@ export const makeUsersRepositoryMock = (value: UsersRepositoryMockValue) => {
       findUserByExternalId instanceof Error
         ? jest.fn<Promise<void>, []>().mockRejectedValue(findUserByExternalId)
         : jest.fn<Promise<User>, []>().mockResolvedValue(findUserByExternalId),
+    existsAuthorId:
+      existsAuthorId instanceof Error
+        ? jest.fn<Promise<void>, []>().mockRejectedValue(existsAuthorId)
+        : jest.fn<Promise<boolean>, []>().mockResolvedValue(existsAuthorId),
   };
 };
 
@@ -332,5 +338,6 @@ export const makeDefaultUsersRepositoryMockValue =
       createNormalUser: newUser,
       findSameAccountUsers: [user1, user2],
       findUserByExternalId: newUser,
+      existsAuthorId: false,
     };
   };
diff --git a/dictation_server/src/features/users/users.service.spec.ts b/dictation_server/src/features/users/users.service.spec.ts
index 69543b8..bc1a693 100644
--- a/dictation_server/src/features/users/users.service.spec.ts
+++ b/dictation_server/src/features/users/users.service.spec.ts
@@ -460,7 +460,46 @@ it('メールアドレスが重複している場合、エラーとなる。', a
     new HttpException(makeErrorResponse('E010301'), HttpStatus.BAD_REQUEST),
   );
 });
-it('AuthorIDが重複している場合、エラーとなる。', async () => {
+it('AuthorIDが重複している場合、エラーとなる。(AuthorID重複チェックでエラー)', async () => {
+  const cryptoMockValue = makeDefaultCryptoMockValue();
+  const usersRepositoryMockValue = makeDefaultUsersRepositoryMockValue();
+  const adb2cParam = makeDefaultAdB2cMockValue();
+  const sendgridMockValue = makeDefaultSendGridlValue();
+  const configMockValue = makeDefaultConfigValue();
+  usersRepositoryMockValue.createNormalUser = new Error();
+  usersRepositoryMockValue.existsAuthorId = true;
+
+  const service = await makeUsersServiceMock(
+    cryptoMockValue,
+    usersRepositoryMockValue,
+    adb2cParam,
+    sendgridMockValue,
+    configMockValue,
+  );
+  const name = 'test_user8';
+  const role = 'Author';
+  const email = 'test8@example.co.jp';
+  const autoRenew = true;
+  const licenseAlert = true;
+  const notification = true;
+  const authorId = 'testID';
+  const token: AccessToken = { userId: '0001', role: '' };
+  await expect(
+    service.createUser(
+      token,
+      name,
+      role,
+      email,
+      autoRenew,
+      licenseAlert,
+      notification,
+      authorId,
+    ),
+  ).rejects.toEqual(
+    new HttpException(makeErrorResponse('E010302'), HttpStatus.BAD_REQUEST),
+  );
+});
+it('AuthorIDが重複している場合、エラーとなる。(insert失敗)', async () => {
   const cryptoMockValue = makeDefaultCryptoMockValue();
   const usersRepositoryMockValue = makeDefaultUsersRepositoryMockValue();
   const adb2cParam = makeDefaultAdB2cMockValue();
@@ -476,9 +515,9 @@ it('AuthorIDが重複している場合、エラーとなる。', async () => {
     sendgridMockValue,
     configMockValue,
   );
-  const name = 'test_user8';
+  const name = 'test_user9';
   const role = 'Author';
-  const email = 'test8@example.co.jp';
+  const email = 'test9@example.co.jp';
   const autoRenew = true;
   const licenseAlert = true;
   const notification = true;
diff --git a/dictation_server/src/features/users/users.service.ts b/dictation_server/src/features/users/users.service.ts
index d56e0e8..a80a9df 100644
--- a/dictation_server/src/features/users/users.service.ts
+++ b/dictation_server/src/features/users/users.service.ts
@@ -114,6 +114,28 @@ export class UsersService {
 
     const accountId = adminUser.account_id;
 
+    //authorIdが重複していないかチェックする
+    if (authorId) {
+      let isAuthorIdDuplicated = false;
+      try {
+        isAuthorIdDuplicated = await this.usersRepository.existsAuthorId(
+          accountId,
+          authorId,
+        );
+      } catch (e) {
+        throw new HttpException(
+          makeErrorResponse('E009999'),
+          HttpStatus.INTERNAL_SERVER_ERROR,
+        );
+      }
+      if (isAuthorIdDuplicated) {
+        throw new HttpException(
+          makeErrorResponse('E010302'),
+          HttpStatus.BAD_REQUEST,
+        );
+      }
+    }
+
     // ランダムなパスワードを生成する
     const ramdomPassword = makePassword();
 
diff --git a/dictation_server/src/repositories/users/users.repository.service.ts b/dictation_server/src/repositories/users/users.repository.service.ts
index 6318a9a..da1ad6d 100644
--- a/dictation_server/src/repositories/users/users.repository.service.ts
+++ b/dictation_server/src/repositories/users/users.repository.service.ts
@@ -122,6 +122,30 @@ export class UsersRepositoryService {
     return user;
   }
 
+  /**
+   * AuthorIdが既に存在するか確認する
+   * @param user
+   * @returns 存在する：true 存在しない：false
+   */
+  async existsAuthorId(
+    accountId: number,
+    authorId: string,
+  ): Promise<boolean | undefined> {
+    const user = await this.dataSource.getRepository(User).findOne({
+      where: [
+        {
+          account_id: accountId,
+          author_id: authorId,
+        },
+      ],
+    });
+
+    if (user) {
+      return true;
+    }
+    return false;
+  }
+
   /**
    * 特定の情報でユーザーを更新する
    * @param user