To provide an oil pump arrangement structure which can prevent oil from being agitated by an oil pump drive gear on a double support type oil pump drive shaft without providing a baffle plate.

The oil pump arrangement structure includes: an oil pump drive shaft gear 26 in which one end side is supported by a flywheel case 29, and the other end side is supported by a control body 34, and which is coupled to the oil pump 23; and a gear chamber 37 which covers the gear 26. The control body 34 is coupled to the flywheel case 29 through a separate plate 35. The gear chamber 37 is formed of the flywheel case 29 and an agitation prevention rib 33, which cover one side surface and the lower part of the outer periphery of the oil pump drive gear 26, and the separate plate 35 and an extension part 35a thereof, which cover the other side surface of the oil pump drive gear 26.