There is provided a system for judging validity of a radio terminal according to identification information on the radio terminal and providing a service. A radio network is divided into a plurality of zones. For each of the zones, there is arranged a server for storing in a particular zone, the position of the directory containing identification information on each radio terminal without storing identification information on the radio terminal registered in other zone. By communication between the server and zone controllers, the identification information on the radio terminal is confirmed and a service is provided. Thus, it is possible to realizing a roaming system capable of performing an ideal roaming without increasing the volume of the system resource.