To provide an oil pump and a manufacturing method therefor capable of improving the workability in manufacturing and reducing its weight.

This oil pump is provided with an oil pump body and an oil pump cover 12 attached to oil pump body. Oil passages 19, 20 are formed in the oil pump cover 12 by casting in a pipe 21, and a substantially central part or its vicinity of the pipe 21 is cast in while it is exposed. The pipe 21 consists of an exposed part 22 in which a pipe 21 skin is exposed and an embedding part 23 covering the pipe 21 skin and is exposed on an abutting face of the oil pump cover 12 and a face on the opposite side to it. Consequently, the workability can be improved when the oil pump cover 12 and the oil pump are manufactured and its weight can be reduced by casting in the pipe 21 and forming the exposed part 22 in the pipe 21 in this way.