In a receiving circuit 44 for receiving an electromagnetic wave signal, a frequency converter/detector circuit 100 comprises a local oscillator 131 for generating an oscillation signal, plural mixers 133, 134 for mixing the received electromagnetic wave signal with the oscillation signal to generate intermediate frequency signals having different phases, and a signal generating/synthesizing circuit 140 for generating based on the intermediate frequency signals generated by the mixers other intermediate frequency signals which are different in phase from the original intermediate frequency signals, for detecting the intermediate frequency signals and other intermediate frequency signal, and for adding the detected signals together to generate a synthesized signal.