For processing an uplink signal from a mobile station without desiring a high AFC capability in any state, in a wireless base station including a plurality of antennas, reception signals from a mobile station are taken in to perform a signal transmission and reception with the mobile station by a first antenna providing a higher reception signal level, in which a switchover from a signal transmission to the mobile station by the first antenna to that by a second antenna is performed when a frequency variation characteristic measured for an allocated frequency of the reception signal from the first antenna indicates that the mobile station is moving away from the first antenna.