A series resonance circuit defined by a series circuit including an inductor and a capacitor and a series resonance circuit defined by a series circuit including an inductor and a capacitor are connected in shunt to a signal line. A diode is disposed between the grounding end of the series resonance circuit and the ground, and a diode is disposed between the grounding end of the series resonance circuit and the ground. The connection point between the grounding end of the series resonance circuit and the diode is connected to the ground via a frequency shifting inductor in a conductive state at high frequency, and the connection point between the grounding end of the series resonance circuit and the diode is connected to the ground via a frequency shifting inductor in a conductive state at high frequency. A matching circuit defined by a multistage T-shape LCL circuit is disposed between the series resonance circuits.