Plasma processing method

In the present invention, provided is a plasma processing method which reduces or eliminates the emission of contaminating matters caused by a quality-altered layer on the surface of yttria of a processing chamber's inner wall and parts inside the processing chamber. It is the plasma processing method including an etching step of setting a sample inside the processing chamber, and etching the sample, a deposition-product removing step of removing a deposition product by using a plasma, the deposition product being deposited inside the processing chamber by the etching step, the plasma being generated using a gas which contains fluorine or chlorine, and a step of exposing, to a rare-gas-based plasma, the inside of the processing chamber after the deposition-product removing step.