Cleaning method

A method for cleaning a microwave plasma processing apparatus which has a processing container and a microwave radiation part, and which has a window part provided at a position where the microwave radiation part is disposed in the processing container, the method comprising:

• a cleaning step of adjusting an internal pressure of the processing container, based on a correlation between the internal pressure and a plasma diffusion distance of plasma generated by the microwave radiation part, to a pressure corresponding to the plasma diffusion distance for a plasma region to reach a cleaning target part, among parts within the processing container including a wall surface of the processing container, the microwave radiation part, and the window part, while supplying a cleaning gas, and performing a cleaning process using plasma of the cleaning gas,
• wherein the cleaning step comprises:
• a first step of adjusting the internal pressure to a first pressure, which corresponds to a first plasma diffusion distance for the plasma region to reach a first cleaning target part, and performing the cleaning process;
• and
• a second step of adjusting the internal pressure to a second pressure, which corresponds to a second plasma diffusion distance for the plasma region to reach a second cleaning target part having a different size than the first cleaning target part, and is different from the first pressure, and performing the cleaning process.