A plasma processing apparatus includes a slot plate of an antenna and the slot plate has slots arranged in a circumferential direction thereof with respect to an axis line. A microwave is introduced into a processing space from the antenna via a dielectric window, and a through hole is formed in the dielectric window along the axis line. A plasma processing method performed in the plasma processing apparatus includes performing a first cleaning process by radiating the microwave from the antenna and supplying a cleaning gas from a cleaning gas supply system; and performing a second cleaning process by radiating the microwave from the antenna and supplying the cleaning gas from the cleaning gas supply system. A first pressure of the processing space in the performing of the first cleaning process is set to be lower than a second pressure thereof in the performing of the second cleaning process.