PURPOSE:To attain the automatic equalization of the primary and the secondary amplitude distortion by a detecting signal, by detecting the amplitude distortion of an IF signal spectrum. CONSTITUTION:An IF signal receiving the amplitude distortion due to fading at an input terminal 1 is inputted to an HYB2, and inputted to an HYB8 via a delay line 3, HYB5 and a delay line 7, then a main signal is outputted from the HYB5, an advanced wave is outputted from the HYB2 and a delay wave is outputted from the HYB8 respectively. The progressing wave and the delay wave are inputted respectively to variable phase shifters 10, 11 and the phase is set to a prescribed value. The output of the variable phase devices 10, 11 is synthesized at an HYB12 and set to a prescribed amplitude at a variable attenuator 13. The output of the attenuator 13 is inputted to an HYB14, synthesized with the main wave of the HYB5 and the IF signal having the amplitude distortion is equalized into a prescribed wave form and outputted from an output terminal 9.