Each of a first high frequency power supply and a second high frequency power supply of a plasma processing apparatus is configured to selectively output a continuous wave, a modulated wave and a double-modulated wave. A first average value which determines an impedance at a load side of the first high frequency power supply and a second average value which determines an impedance at a load side of the second high frequency power supply are obtained by using any one of two averaging methods depending on a first high frequency power output from the first high frequency power supply and a second high frequency power output from the second high frequency power supply. An impedance matching of each of a first matching device and a second matching device is performed based on the first average value and the second average value.