A plasma processing apparatus includes: a processing container; a ceiling wall forming a part of the processing container and including an opening; and a transmission window configured to close the opening, wherein the opening under the transmission window is formed as a recess portion, wherein the recess portion is a supply port for supplying electromagnetic waves from the transmission window into the processing container, wherein first gas supply holes are formed on a lower surface of the ceiling wall, and wherein second gas supply holes are formed on an inner surface of the recess portion.