Abstract: A communication system for allowing communications as of Internet and the like to be universally used without restricting a second user to use communication and further without requiring any significant capital investment. According to this communication system, when a terminal (104) becomes able to communicate with a network usage terminal (101) and is about to use the Internet via the network usage terminal (101), it transmits the authentication information of its user (B), and the network usage terminal (101) then transmits the authentication information of its owner (A) and the received authentication information of the user (B) to an authentication server (105). If a result of authentication is OK, the network usage terminal (101) relays the communication of the terminal (104) to the Internet (103), thereby permitting the terminal (104) to use the Internet.