Disclosed is a reordering method for sending packets, to which numbers indicating sequence are attached, from a base station to a mobile station, and rearranging the packets in order of the sequence number in the mobile station. When a handover source base station transfers packets which have not been sent to the mobile station, out of packets received from a host station, to a handover target base station, and the handover target base station sends the packets to the mobile station, data is sent from the handover source base station to the mobile station to notify that transference of the packets has been executed at the execution of handover sequence. The mobile station executed, reordering of the received packets when the transference of the packets has been executed.