To provide an small-sized oil pump ensuring reliability by preventing a non-lubrication condition in the oil pump having possibility of sucking air from a suction port.

In this oil pump 100 having a housing 30 forming a first cylindrical space 31, a first driven rotor 40 arranged rotatively in the space, a first drive rotor 50 arranged on the inner periphery of the rotor and forming two or more volumetric chambers R with volume contracted/expanded between the rotors, a discharge port 12 communicating with the contracted side volumetric chamber of the volumetric chambers and two or more suction ports 11a, 11b communicating with the expanded side volumetric chamber, partitioning sections 13, 23 sectioning the adjacent suction ports 11a, 11b and extending in the radial direction of the drive rotor 50 are formed between the adjacent suction ports 11a, 11b of two or more suction ports 11a, 11b, and independent suction passages 14a, 14b communicating with an oil storage section 60 are respectively arranged in the suction ports 11a, 11b.