Abstract: In a vacuum processing apparatus comprising a reactor and a vacuum pump connected to the reactor to draw up a gas held in the reactor, the vacuum pump comprising a diffusion pump and an auxiliary pump, the diffusion pump and the auxiliary pump are connected through an exhaust line and a cooling unit is provided in the exhaust line, whereby the gas is cooled by the cooling unit to liquefy or condense an oil smoke comprised of a diffusion pump oil contained in the gas, to cause the resultant oil to deposit in the exhaust line. The diffusion pump oil can be prevented from flowing into the auxiliary pump even when material gases fed in at a high rate are exhausted.