PURPOSE: To obtain a matching circuit suitable for the transmission of a transmission signal of large power, by using a reactance tube for a circuit network for impedance matching.

CONSTITUTION: Matching circuits 10-1, 10-2 are connected between a transmission output circuit 1 and an antenna 6. The matching circuits consist of the reactance tube and a matching capacitor C using an FET10. The capacitance of the FET10 is changed by changing a gate voltage. Thus, a variable capacitance of the FET is added to the matching capacitor C by changing the gate voltage of the FET10, the matching between the antenna circuit and a transmitter output circuit is done easily.