Mechanical pump

Patent Pending PROBLEM TO BE SOLVED: To provide a mechanical pump capable of suppressing the occurrence and accumulation of reaction products and ensuring a normal operation over a long period of time. ; SOLUTION: This mechanical pump has an yttria (Y<SB>2</SB>O<SB>3</SB>) film on the surface of a gas contact part exposed to gas inside a casing a3 which should be exhausted.