An oil pump includes: a shaft member; an inner rotor configured to rotate integrally with the shaft member; an outer rotor forming a rotor chamber into which oil is sucked from a suction passage and from which the oil is discharged toward a discharge passage, between the inner rotor and the outer rotor; a body member having a recess-shaped housing chamber in which each rotor is housed so as to be rotatable about an axis; and a cover member attached so as to close the housing chamber. The rotor chamber has first and second suction ports through each of which the oil to be sucked from the suction passage passes. The oil pump includes a straightening member branching the suction passage from a main path to the first suction port side and the second suction port side.