To reduce the distortion of a signal output from an amplifier even if a signal input to the amplifier is a signal with power greater than estimated power.

An antenna 10 connects a plurality of terminal devices. A PA 24 amplifies an RF signal to be transmitted and outputs a final output signal 208. A baseband processing unit 14 carries out modulation/demodulation processing, adaptive array processing and the like. A transmission frequency converting unit 60 performs digital/analog conversion on a baseband transmission signal 202 and frequency-converts it into the RF signal to be transmitted. A transmission gain control unit 28 controls power of the RF signal to be transmitted on the basis of a gain control signal 204 and inputs the signal to the PA 24. A detection unit 30 inputs the final output signal 208, detects it, and outputs a detecting signal 206.