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, includes a cleaning step of adjusting a pressure to a pressure corresponding to a size of 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.