A plasma processing apparatus includes a microwave introducing module provided at a ceiling portion of a processing chamber and configured to introduce a microwave for generating plasma of a gas into the processing chamber; and a plurality of gas supply holes formed at the ceiling portion of the processing chamber and configured to introduce the gas into a plasma processing space. Each of the plurality of gas supply holes includes a fine hole and a cavity that is expanded from the fine hole and opened to the plasma processing space. A diameter of the cavity on the plasma processing space side is 3 mm or more and is ⅛ or less of a wavelength of a surface wave of a microwave in the plasma.