Plasma processing apparatus

A plasma processing apparatus comprising:

• a chamber;
• a radio-frequency power supply;
• an electrode electrically connected to the radio-frequency power supply in order to generate plasma in the chamber;
• and
• a matching device connected between the radio-frequency power supply and the electrode,
• wherein the radio-frequency power supply outputs radio-frequency power generated such that a power level during a first period is higher than a power level during a second period alternating with the first period,
• the matching device sets a load side impedance of the radio-frequency power supply during a monitoring period within the first period to an impedance that differs from an output impedance of the radio-frequency power supply, the monitoring period is a period starting after a predetermined time length elapses from a start point of the first period, and
• the radio-frequency power supply adjusts the power level of the radio-frequency power such that a load power level, which is a difference between a power level of a traveling wave and a power level of a reflected wave, becomes a designated power level.