Disclosed is a technique which reduces the packet loss and the band consumption for data transfer when a mobile terminal conducts the handover between a fixed base station and a mobile base station for group movement. According to this technique, when an MH (mobile terminal) 320 conducts the handover from a fixed base station (E-LSR 230) positioned at an edge of an access network 200 to a mobile base station (MEB 310) located in a train or the like, a predetermined flag is appended to a frame addressed to the MH in a label switching router (P-LSR 210) positioned at a core network 100 side edge of the access network. The frame having the appended flag is copied in the E-LSR 230. One frame after copied is transmitted directly from the E-LSR to the MH while the other frame after copied is transferred from the E-LSR to the MEB and then transmitted from the MEB to the MH, thus realizing the soft handover.