Plasma processing apparatus

A plasma processing apparatus of generating plasma by high frequency discharge of a processing gas within a decompression processing vessel that accommodates therein a processing target object, which is loaded into and unloaded from the processing vessel, and performing a process on the processing target object within the processing vessel with the plasma, the plasma processing apparatus comprising:

• a first high frequency power supply configured to output a first high frequency power;
• a first high frequency power modulation unit configured to pulse-modulate an output of the first high frequency power supply with a modulation pulse having a regular frequency such that the first high frequency power has a high level during a first period and has a low level lower than the high level during a second period, the first period and the second period being repeated alternately with a preset duty ratio;
• a first high frequency transmission line configured to transmit the first high frequency power outputted from the first high frequency power supply to a first electrode provided within or in the vicinity of the processing vessel;
• and
• a first matching device configured to measure a load impedance on the first high frequency transmission line with respect to the first high frequency power supply, and configured to match a weighted average measurement value, which is obtained by weighted-averaging a load impedance measurement value during the first period and a load impedance measurement value during the second period with a preset weighted value, with an output impedance of the first high frequency power supply.