noun
advertising company; ad agency
A company that plans, creates, and places advertisements for clients.
彼は大手の広告会社に勤めている。
He works for a major advertising company.
Often used interchangeably with 広告会社, but 広告代理店 may emphasize the agency role of representing media on behalf of advertisers.
Compound of 広告 (advertisement) + 会社 (company).