To realize global roaming only through an existent Mobile IP procedure in an independent network based on Mobile IP.

In the mobile terminal MN, an interface IF1 of higher priority is selected from interfaces IF1 and IF2 which can be connected to a communication network in accordance with given priority, a connection base station FA2 that is not selected, is virtually formed inside the relevant mobile terminal MN, and a transfer path via a transfer management base HA1 of a mobile backbone 2 is registered through the selected interface IF1 and the virtually formed connection base station FA2 to a transfer management base HA2 of a mobile backbone 1, so that data received in the transfer management base HA2 via an opposite party terminal CN are transmitted to the mobile terminal MN via the transfer management stations HA1 and FA1.