MATCHING BOX AND MATCHING METHOD

A matching box comprises a directional coupler that detects forward waves and reflected waves; a matching circuit having a first variable capacitance capacitor, a second variable capacitance capacitor, and inductance; and a control unit that calculates a reflection coefficient on the basis of the forward waves and the reflected waves, and controls a capacitance value VC1 of the first variable capacitance capacitor and a capacitance value VC2 of the second variable capacitance capacitor, wherein the control unit changes VC2 if the distance between a matching circle drawn by the trajectory of the reflection coefficient passing through a matching point on a Smith chart, and the calculated reflection coefficient is greater than a prescribed value, and changes VC1 if such distance is set to be no greater than the prescribed value and when the value of such distance becomes no greater than the prescribed value, thereby reducing the reflection coefficient.