A quadrature detector subjects a received signal to quadrature detection and outputs a base band signal. A direct current component measurement circuit measures a magnitude of a direct current component included in the base band signal from the quadrature detector. A first HPF and a second HPF reduce the direct current component included in the base band signal from the quadrature detector. A demodulator demodulates the base band signal output from the first HPF and the second HPF. A controller exercises control to attenuate a level of the received signal input to the quadrature detector when the magnitude of the direct current component measured by the direct current component measurement circuit is equal to or larger than a threshold value.