A content server 10, in transmitting content appended with redistribution restriction information to a communication terminal 50, determines whether communication terminal 50 has a redistribution restriction function on the basis of identification data contained in a user agent header contained in a HTTP message transmitted from communication terminal 50. When the determination is affirmative, content server 10 transmits to communication terminal 50 the content via the Internet 20, gateway server 30, and mobile packet communication network 40.