PURPOSE: To prevent lip wear in an oil seal from occurring, by installing an empty space in the point midway in a lubricating hole feeding lubricating oil to the inside a vacuum pump as an oil pan, and also installing an empty space in the point midway in a suction pressure hole, making a back part of the oil seal suction pressure, as a damper.

CONSTITUTION: In a vacuum pump, there is provided with an oil seal 3 for preventing lubricating oil passing through a metal bearing 4 from a lubricating hole 10 from flowing out into a generator and keeping sealability in the vacuum pump. And, the oil seal 3 is designed in a manner confortable to suction pressure to reduce its lip wear, while an inner part 6' of the vacuum pump is interconnected to a back part 3' of the oil seal 3 through a suction pressure hole 9 so as to make the back part 3' of the oil seal 3 suction pressure. In the above-mentioned, an empty space 12 is installed in the point midway in the lubricating hole 10 as an oil pan at which foreign substances being large in grain size are all deposited and removed therefrom. Likewise, another empty space 11 is installed in the point midway in the suction pressure hole 9 as a damper at which pressure variations in time of air intake into the inside 6' of the vacuum pump are relieved.