As a capacitor Cj is connected in parallel to a non-reciprocal circuit 3, in a predetermined frequency band in which a power amplifier 2 is used, or in other words, in a predetermined frequency band used in communication, an input impedance of the non-reciprocal circuit 3 is adjusted and the length of an impedance curve (reflection coefficient S11) at an input terminal P2 of the non-reciprocal circuit 3 can thus be reduced. In addition, an output impedance of the power amplifier 2 and an input impedance of the non-reciprocal circuit 3 can be matched in a broad band through an interstage matching circuit 7 (input matching circuit 6) provided between an output terminal P1 of the power amplifier 2 and the input terminal P2 of the non-reciprocal circuit 3.