A communication system in which, even when an HTTP session is disconnected from a mobile device, the HTTP session can be continued or a response from a Web server can be returned to a user, without installing a special application in the mobile device. A load-distributable system is provided for realizing such operation. To that end, in a communication system having a relay device that relays a request from a portable telephone terminal (110) to a Web server (120), the relay device (130) relays a processing request from the portable telephone terminal (110) to the Web server, and stores a processing response from the Web server. The relay device (130) sends the portable telephone terminal a message to the effect that the processing response should be acquired from the relay device (130) or a message with the processing response added.