PURPOSE: To realize the high frequency attenuation circuit employing a PIN diode in which the attenuation at a high frequency is increased even when a current fed to the PIN diode is small.

CONSTITUTION: An inductance element L1 in parallel resonance with a terminal capacitance of a PIN diode D is added in parallel with the PIN diode D and the circuit is in parallel resonance at a desired high frequency to increase the attenuation and the dynamic range of the attenuation at the desired high frequency is increased, A capacitor C1 in series connection with the PIN diode D is a DC blocking bypass capacitor.