An oil pump includes: an annular stator (2) having coils (22); a cylindrical outer rotor (3) having a plurality of permanent magnets (24); an inner rotor (4) positioned eccentrically to an inner peripheral side of the outer rotor (3); six linkage plates (5) which link between the outer rotor (3) and the inner rotor (4); and a drive shaft (6) on which the inner rotor (4) is attached. A pump action is obtained by rotating the outer rotor (3) and the inner rotor (action is obtained by rotating the outer rotor (3) and the inner rotor (4). Each of linkage plates (5) has a symmetrical cross sectional shape. A torque transmission is possible in the same way even if the outer rotor (3) is at a drive side and even if the inner rotor (4) is at the drive side.

An electric oil pump includes an electric motor and an oil pump that is driven by the motive power from an electric motor, wherein; the oil pump has an introducing channel that guides a drain oil that has leaked from an interior of the oil pump to an interior of the electric motor; and the electric motor has a discharging channel that discharges the drain oil that has been guided to the interior of the electric motor to a tank.