Network service system using temporary user identifier

A network service system of the present invention comprises a temporary user identifier update request transmitting side device which provides a first service to a user and can transmit a request to update a temporary user identifier shared within a system; a temporary user identifier update request receiving side device which is connected to the temporary user identifier update request transmitting side device by a network and can receive the update request from the temporary user identifier update request transmitting side device, for providing the second service cooperating with the first service using the updated temporary user identifier; and a user proxy device which is connected to the temporary user identifier update request transmitting side device and the temporary identifier update request receiving side device by the network, and with which the user receives the two services.