An electric pump unit comprising: an outer rotor; an inner rotor which meshes with the outer rotor in such a state that the inner rotor and the outer rotor are placed eccentrically to each other and which is driven by being supported by a rotation shaft of an electric motor; a pump housing which defines a cavity portion which accommodates therein the outer rotor and the inner rotor; inlet and outlet ports (13a, 13b) which are provided on inlet and outlet sides, respectively, so as to suck and discharge a fluid and which communicate with each other via the cavity portion; and fluid circulating means for circulating the fluid from the outlet side to the inlet side when a fluid pressure at the outlet side reaches or exceeds a predetermined pressure, wherein the fluid circulating means is a relief valve which is provided so as to face the inlet and outlet ports, characterized in that a pump plate is provided so as to seal the cavity portion, crescent-shaped oil passages (13ri, 13ro) are formed at the inlet and outlet sides, respectively, so as to extend along outer circumferential circular arcs of the inner rotor and the outer rotor, the inlet and outlet ports (13a, 13b) are formed in the pump plate in such a manner as to extend in the same direction along predetermined axes so as to communicate with the oil passages (13rii, 13ro), respectively, and the relief valve is provided in the pump plate in such a state that an axis in an operating direction of the relief valve is made to intersect the axes of the inlet and outlet ports (13a, 13b) substantially at right angles in a plane which intersects the rotating shaft of the electric motor at right angles and in such a manner as to operatively communicate with the respective oil passages (13ri, 13ro) without communicating with the inlet and outlet ports. an outer rotor; an inner rotor which meshes with the outer rotor in such a state that the inner rotor and the outer rotor are placed eccentrically to each other and which is driven by being supported by a rotation shaft of an electric motor; a pump housing which defines a cavity portion which accommodates therein the outer rotor and the inner rotor; inlet and outlet ports (13a, 13b) which are provided on inlet and outlet sides, respectively, so as to suck and discharge a fluid and which communicate with each other via the cavity portion; and fluid circulating means for circulating the fluid from the outlet side to the inlet side when a fluid pressure at the outlet side reaches or exceeds a predetermined pressure, wherein the fluid circulating means is a relief valve which is provided so as to face the inlet and outlet ports, characterized in that a pump plate is provided so as to seal the cavity portion, crescent-shaped oil passages (13ri, 13ro) are formed at the inlet and outlet sides, respectively, so as to extend along outer circumferential circular arcs of the inner rotor and the outer rotor, the inlet and outlet ports (13a, 13b) are formed in the pump plate in such a manner as to extend in the same direction along predetermined axes so as to communicate with the oil passages (13rii, 13ro), respectively, and the relief valve is provided in the pump plate in such a state that an axis in an operating direction of the relief valve is made to intersect the axes of the inlet and outlet ports (13a, 13b) substantially at right angles in a plane which intersects the rotating shaft of the electric motor at right angles and in such a manner as to operatively communicate with the respective oil passages (13ri, 13ro) without communicating with the inlet and outlet ports.