There is provided a microwave plasma source for radiating microwaves into a chamber of a plasma processing apparatus to generate surface wave plasma, including: a plurality of microwave radiation mechanisms provided in a ceiling wall of the chamber and configured to radiate microwaves into the chamber; and a perforated plate provided in a high electric field formation region used as a high electric field region when the microwaves are radiated from microwave radiation surfaces of the microwave radiation mechanisms into the chamber and which exists just below the microwave radiation surfaces. The perforated plate has a function of confining surface waves formed just below the microwave radiation surfaces when the microwaves are radiated from the microwave radiation mechanism, in a space surrounded by the microwave radiation surfaces and the perforated plate, and a function of keeping high a power absorption efficiency of plasma generated in the space.