A mobile communication system which can transfer information on the number of packets counted up until then by a base station of a mobile source, to a base station of a mobile target, even when a terminal performs a handover. UE moves to a Target eNode B, but a Source eNode B decides to perform a handover, and the Source eNode B includes information on the number of packets counted up until then in a Handover Request message to the Target eNode B, so as to notify the Target eNode B. After receiving a Handover Confirm message from the UE, the Target eNode B includes information on the number of packets received from the Source eNode B in a Handover Complete message transmitted to a CN Node, so as to notify the CN Node.