Gas processing apparatus

Patent Pending PROBLEM TO BE SOLVED: To provide a gas processing apparatus using a material that can suppress entry of a corrosive gas than in comparison with a conventional apparatus and can prevent an element in a substrate from entering a surface layer, and to provide a mechanical pump. SOLUTION: Gas passes through and resides in the apparatus where a portion contacting with the gas includes a substrate having Fe, a barrier film provided on the surface of the substrate and prevents the Fe from spreading, and a surface protective film that is provided on the barrier film and mainly composed of at least yttria.