Handover apparatus and method in mobile communication system

A handover apparatus, a method and a system thereof in a mobile communications system are provided to transmit a frame number and perform a handover smoothly. A measurement about a target base station(Target eNB) of a target cell in which a terminal handovers. A measurement report message set up as the system frame number does not existed is transmitted to a source base station(461). A handoff request message which is set up as the system frame number does not existed is transmitted(463). A handover request acknowledgement message is transmitted to the source base station(465). The source base station transmits the handover command message to the terminal(467). The transfer frame of the random access control channel is calculated. The terminal transmits the code of the random access control channel to the target base station.