A plasma processing apparatus includes: a processing container; a ceiling plate that constitutes a ceiling wall of the processing container, is formed of a first dielectric, and has an opening formed in the first dielectric; at least one transmissive window disposed in the opening and formed of a second dielectric having a second permittivity greater than a first permittivity of the first dielectric; and at least one electromagnetic wave supplier configured to supply electromagnetic waves toward the at least one transmissive window.