Plasma processing apparatus

A plasma processing apparatus includes: a coaxial tube that is provided so as to extend in a vertical direction and forms a part of a high-frequency waveguide; a substrate supporting part which is used for supporting the substrate; an electrode having a gas flow path connected to a gas discharge port that opens to a space above the substrate support unit, the electrode being provided above the substrate support unit and having an inner conductor of the coaxial tube connected to the center thereof; an expanded-diameter part which forms a part of the high-frequency waveguide together with the electrode and is connected to an outer conductor of the coaxial tube; and a plurality of dielectric tubes which are connected to the electrode so as to pass through a space between the electrode and the expanded-diameter section and which are formed of a dielectric so as to supply a gas to the electrode, the plurality of dielectric tubes being provided so as to be dispersed in the space between the electrode and the expand