A high performance demodulator able to realize a further wide band property, low distortion characteristics, and low power consumption in comparison with a conventional multi-port demodulator and having a small fluctuation in characteristics with respect to temperature fluctuations and aging and comprising a five-port junction circuit 101 receiving a received signal Sr and a local signal Slo generated at a local signal generation circuit 102, generating three signals having a phase difference, detecting signal levels (amplitude components) of these signals to obtain three power detection signals (baseband signals) P1, P2, and P3; a first multiplier 103 for multiplying the power detection signal P1 output from a first power detector of the five-port junction circuit 101 by a coefficient A1 (=" "(k21/k11) 2 ) for canceling square components of an interference signal and a local signal; a second multiplier 104 for multiplying the power detection signal P1 output from the first power detector by a coefficient A2 (="(k31"/k11) 2 ) for canceling square components of an interference signal and a local signal; a first subtractor 105 for subtracting a multiplication result of the first multiplier 103 from the power detection signal P2 output from a second power detector of the five-port junction circuit 101; a second subtractor 106 for subtracting the multiplication result of the second multiplier 104 from the power detection signal P3 output from a third power detector of the five-port junction circuit 101; and a multi-port signal-to-IQ signal conversion circuit 109 for converting the result to an In-phase signal I and a quadrature signal Q as demodulated signals based on the output signals of the first subtractor 105 and the second subtractor 106. <IMAGE>