To cool the inside of a pump housing effectively, prevent a rotor lock due to a thermal expansion of the rotor and housing caused by temp. rise of the inside of the housing, and solve such problems as shortening of the oil seal lifetime, increase in the required power, etc.

A vacuum pump 1 is composed of a lubricant oil pump 2 consisting of a timing gear 13 installed in an oil chamber 16 and supplying lubricating oil circulativeiy, the first circulative piping 31 in communication with the oil chamber and supplying the lubricating oil, a cooling means 4 to cool the lubricating oil supplied through the first piping 31, and the second circulative piping 32 which cools the inside of the pump housing 10 with the cooled lubricant and feeds the lubricant by pressure to the oil chamber.