A mobile communication system with which the time required for handover is short and which has a superior network operating efficiency. In the mobile communication system of the present invention, each wireless base station measures the strength of the radio waves received from a wireless terminal irrespective of whether or not the destination of the radio waves is the wireless base station itself. The respective wireless base stations mutually provide the radio wave strength measurement result. The wireless base stations replies to the request for handover from wireless terminal only when the radio wave of itself is strongest. In addition, when the processing load is large, the wireless base station selects another wireless base station for which the radio wave strength from the wireless terminal is large and switches the connection.