PURPOSE: To enhance durability of a pump, by providing a filtering material in a housing of the vacuum pump or a fuel pump equipped to an automobile or the like so as to remove impurities from engine oil and supply only the oil to a lubricated surface.

CONSTITUTION: A bottom housing 11 of a vacuum pump is mounted to a head cover of an engine so as to drive a rocker arm 30 by an overhead cam shaft 41. While a cylinder liner 12 integrally provides in its bottom part an inward facing flange 12b, forcing a filtering material 16, consisting of porous material such as a wire net, to be attached and fixed to this inward facing flange 12b by a spring 17. Then the pump is operated so as to filter engine oil jetted from inside the head cover and supply only the oil to a sliding surface between a piston 21 and the cylinder liner 12.