<p>A radio communication network system which comprises an HA (home agent) of a mobile terminal and a plurality of relay devices one of which is registered in the HA as an FA (foreign agent) of the mobile terminal for relaying the communication between the mobile terminal and the HA and allows the mobile terminal to switch between the communication state and standby state of the communication with the HA. Each of the relay devices has a reception section for receiving a state change notification indicating the switching from the standby state to the communication state from the mobile terminal in the standby state which is located in the range managed by its own device and a procedure implementing section for, if the own device is not the FA of the mobile terminal when the state change notification is received, implementing a procedure for making the own device the FA of the mobile terminal in place of another relay device with the another relay device registered as the FA of the mobile terminal at that point and with the HA of the mobile terminal.</p>
