An amplifier circuit that amplifies a carrier wave that a transmitting and receiving part has received, and includes a superimposition wave generation part that generates a superimposition wave to be superimposed onto the carrier wave; an amplifying part that adds the carrier wave and the superimposition wave to obtain an amplified carrier wave and outputs the amplified carrier wave; and an amplitude detection part that detects, based on a change in an amplitude value of the carrier wave, that the carrier wave is a predetermined carrier wave that carries a predetermined communication signal. The amplifier circuit outputs the amplified carrier wave when having detected the predetermined carrier wave.