An oil pump is configured to include a rotor, a drive shaft that drives the rotor to rotate, a rotor chamber in which the rotor is contained, an inlet port and an outlet port each provided in the vicinity of the rotor chamber, and a pump cover. The pump cover is made of a resin. On a portion of an outer surface side of the pump cover corresponding to an inner portion, in which oil circulates, of the pump cover, a rib that has an erecting wall shape is provided.