A mobile station in a communication system for sending packets, to which numbers indicating sequence are attached, from a base station to a mobile station and performing delivery of the packets in order of the sequence number in the mobile station, includes a buffer which stores packets received from both a source base station and a target base station; and a control unit which performs the delivery of the stored packets in order of the sequence number at the handover procedure based on information indicating whether packets which are not sent from the source base station to the mobile station, are forwarded from a source base station to a target base station is set, the information being received from the source base station.