Provided is an impedance matching device for matching an impedance between a high-frequency power source and a load. The impedance matching device pertaining to the present invention is provided with: a matching circuit having variable capacitors, a capacitance of which is adjusted by an ON/OFF operation of a plurality of switches; a switch control unit for performing control for causing states of the switches of the variable capacitors to coincide with a target state in order to adjust the capacitance of the variable capacitors; and a switch state evaluation unit for evaluating whether a switch is in a state requiring suppression of a temperature increase. The switch control unit is configured so that when the switch state evaluation unit evaluates that a switch of the variable capacitors is in a state requiring suppression of a temperature increase, control is performed for suspending changing of a switch state of the switch for a set period and suppressing a temperature increase in the switch.