An oil pump includes: a rotor chamber; an outer rotor; and an inner rotor. A partition surface between a starting end side of the intake port and a terminal end side of the discharge port is set as a first seal land. An intake groove portion that projects from the starting end side of the intake port toward the terminal end side of the discharge port and a discharge groove portion that projects from the terminal end side of the discharge port toward the starting end side of the intake port are formed in positions which are located on the first seal land. The intake groove portion and the discharge groove portion are provided in intermediate tooth height direction positions of a meshing location between the inner rotor and the outer rotor.
