An oil pump includes: a rotor 3 for actuating a pump action to suck oil in
a suction passage 24 from a suction port 27 to supply oil to a delivery
passage by way of a delivery port 19; and a flow control valve for
returning an excessive oil from the delivery passage to the suction
passage 24 as a returning flow of oil by way of a bypass passage 29 when
a flow amount of oil is excessive in the delivery passage. A
corrosion-proof member 9 having corrosion resistance is disposed at the
position which faces to the returning flow of oil in the inner wall
surface of at least one of the suction passage 24 and the bypass passage
29. The corrosion-proof member 9 has a discontinuous shape (for example a
V-shape or a U-shape) in a circumferrencial direction of center line P1
in a cross section which intersects the center line P1 at right angles.