Abstract: A vane pump driven by an engine to serve generally as a source of hydraulic fluid pressure for operating a power steering apparatus.A high pressure chamber (13) is formed either in a pump housing (4) or in a cover plate (6) by casting using a core. An end of the pump housing (4) or of the cover plate (6) defines a slide surface (11) with which a rotor (2) and vanes (1) are slidably and directly engaged, thus being formed with delivery ports (12) or suction ports (29). This precludes the need of a side plate, a spring for biasing the side plate against the rotor, and others which have hitherto been indispensable for a vane pump, so that the total number of components parts is reduced.A cam ring (5) is sandwiched between the pump housing (4) and cover plate (6) and locked together to the pump housing (4). This makes it needless to form a bore in the pump housing (4) for accommodating a cam ring and thereby enhances the machinability of such a pump.