A control circuit (16) is configured to detect the impedance P1 of a load (3) and control each of the reactance value L1 of a first variable reactance element (12), the reactance value L2 of a second variable reactance element (14), and the phase shift amount φ of a phase shifter (15) on the basis of the detected impedance P1. Consequently, impedance matching can be achieved even with the phase shifter (15) that performs discrete phase shift control.