An internal gear pump includes a casing, a cover mounted to the casing, a pump chamber defined between the casing and the cover, an internal gear slidably arranged within the pump chamber, an external gear rotatably arranged within the pump chamber and rotatingly driven from the outside to engage with and drive the internal gear, a fixed filler for regulating sliding movements of the internal and external gears and for preventing oil leakage from a high-pressure side to a lower-pressure side within the pump chamber, a suction port formed in the cover and extended circumferentially within the angular range of about 90 degrees, an oil pocket device formed in respective sliding surfaces of the casing and cover, on which the opposite side surfaces of the internal gear slide, the oil pocket device having a plurality of taper lands extended within the radial width of from the root of tooth of the internal gear to the outer peripheral surface of the internal gear between the peripheral wall of the pump chamber and the fixed filler, the bottom surface of each of the taper lands being tapered to become gradually shallow in the rotating direction of the internal gear, thereby producing a wedge film pressure between the opposite side surfaces of the internal gear and the respective sliding surfaces of the casing and the cover.