A plasma processing device processes a substrate by generating plasma using a surface wave formed on a surface of a shower plate by a supplied microwave, which includes a plasma generating antenna equipped with the shower plate for supplying first and second gases into a processing vessel, and a drooping member installed to protrude downward from a lower end surface of the shower plate. An outer surface of the drooping member spreads outward as it goes from a top end to a bottom end thereof. The shower plate includes first and second gas supply holes through which the first and second gases are supplied into the processing vessel, respectively. The first gas supply holes are disposed inward of the outer surface of the drooping member. The second gas supply holes are disposed outward of the outer surface of the drooping member.