A quadrature demodulation circuit includes: first to fourth mixers to receive a modulation signal; a phase shifter to supply to the first and third mixers a first local frequency signal, to supply to the second mixer a second local frequency signal having a designated phase difference relative to the first local frequency signal, and to supply to the fourth mixer a third local frequency signal that is an inverse in phase to the second local frequency signal; a first adder to add a signal output from the first mixer and a signal output from the second mixer and to output a first demodulation signal; and a second adder to add a signal output from the third mixer and a signal output from the fourth mixer and to output a second demodulation signal.