The present invention includes: gain controlling and amplifying means for amplifying a signal received from a mobile station and for outputting the amplified received signal; reception quality measuring means for measuring reception quality of the received signal output from the gain controlling and amplifying means; scheduling means for performing scheduling to allocate a radio resource to the mobile station on the basis of a measurement result at the reception quality measuring means; gain controlling means for controlling a gain of the gain controlling and amplifying means on the basis of the received signal output from the gain controlling and amplifying means to keep an amplitude of the received signal constant; and received power calculating means for calculating an estimate of received input power received from a mobile station on the basis of scheduling by the scheduling means; wherein the gain controlling means controls the gain of the gain controlling and amplifying means on the basis of the received signal output from the gain controlling and amplifying means and on the basis of the estimate of received input power calculated by the received power calculating means to keep the amplitude of the received signal output from the gain controlling and amplifying means constant.