PURPOSE: To suppress the even-number order distortion of a local oscillating signal without using an externally attached component by adding a same phase signal detecting circuit, which executes negative feedback for one part of an intermediate frequency signal output to a double balanced mixing part, to the double balanced mixing part.

CONSTITUTION: When the frequencies of a high frequency (RH) signal inputted to an RF and the inverse of RF' are set at f0, and the frequencies of local oscillating(LO) signal inputted to an LO and the inverse of LO are set at f1, an intermediate frequency(IF) signal outputted in order to constitute a double balance includes f0±f1, 2f0, 2f1, 3f0±f1,.... Among the signals, especially the LO signal has a high power level, therefore the 2f0 component largely exceeds f0±f1 to be the desired IF component. The 2f0 component is fed back to a FETJ7 by a same phase signal detecting circuit 2, and operates as the negative feedback to 2f0 at a phase difference 0°. Thus, the output of the even-number order component of the LO signal in the outputted IF signal can be suppressed.