When a gateway server GWS receives an access demand to an IP server from a cellular phone MS via a mobile packet communication network MPN, the gateway server acquires information corresponding to a hostname included in the access demand from a primary conversion table T1. When the obtained information is a wide area IP address, gateway server GWS relays the access demand to a IP server on the Internet INET on the basis of the wide area IP address. When the obtained information is identification of a closed area network, gateway server GWS further acquires a closed area IP address corresponding to the hostname included in the access demand and relays the access demand to a IP server on the basis of the closed area IP address in the LAN corresponding to the identification of the closed area network.