Provided is a plasma processing apparatus that performs a processing on a processing target object using plasma. The plasma processing apparatus includes a processing container and a plasma generating mechanism including a high frequency generator disposed outside of the processing container to generate high frequency waves. The plasma generating mechanism generates plasma in the processing container using the high frequency waves and includes: a high frequency oscillator that oscillates the high frequency waves; a power supply unit that supplies a power to the high frequency oscillator; a waveguide path that propagates the high frequency waves oscillated by the high frequency oscillator to the processing container side which becomes a load side; and a voltage standing wave ratio variable mechanism that varies a voltage standing wave ratio of voltage standing waves formed in the waveguide path by the high frequency waves, according to the power supplied from the power supply unit.