According to one embodiment, a plasma processing apparatus that includes a process target holding portion and a plasma generating unit in a chamber, and processes a process target by using generated plasma is provided. An yttrium oxide film is formed on an inner wall of the chamber and a surface of a structural member in the chamber on a generation region side of the plasma. The yttrium oxide film includes yttrium oxide particles, has a film thickness of 10 μm or more and 200 μm or less, has a film density of 90% or more, and is such that yttrium oxide particles, which are present in a unit area 20 μm×20 μm and whose grain boundary is confirmable, are 0 to 80% in area ratio.