PURPOSE: To perform mutual synchronization only by autonomous control without depending upon control by a host station by sending priority information regarding synchronism establishment and synchronism establishment information, showing whether or not its station is already synchronized with other radio base stations, by each radio base station by including them in a control signal.

CONSTITUTION: Each radio base station 20 includes the priority information regarding synchronism establishment in the control signal to be sent in addition to the synchronism establishment information showing whether or not the local station is already synchronized with other radio base stations 20. It is decided whether radio base stations which are not synchronized among radio base stations 20 having received the control signal are stations that the opposite station may be synchronized with according to the priority information. The priority is automatically updated into the same priority of the opposite station which is synchronized after the synchronization is performed, and also variable under the control of the host station 30 of the radio base station 20. When the opposite station is the station which may be synchronized and already synchronized, the station is synchronized with the opposite station.