Microwave plasma source and plasma processing apparatus

A microwave plasma source for forming a surface wave plasma by radiating a microwave into a chamber of a plasma processing apparatus, which includes: a microwave output part for outputting the microwave; a microwave transmission part for transmitting the microwave; and a microwave radiation member for radiating the microwave into the chamber. The microwave transmission part includes a plurality of microwave introduction mechanisms circumferentially arranged in a peripheral portion of the microwave radiation member and configured to introduce the microwave into the microwave radiation member. The microwave radiation member includes a metal main body, a plurality of dielectric slow-wave members arranged in an overall annular shape in the vicinity of an arrangement surface of the main body, an annular dielectric microwave transmission member arranged in a microwave radiation surface of the main body, and a slot antenna part installed between the slow-wave members and the microwave transmission member.