To provide an oil groove machining method for forming an oil groove in an arbitrary part on a surface of a bore simply while holding shape precision of the bore of a cylinder.

This oil groove machining method comprises a process for machining the bore 10 up to rough dimension ψby leaving finish grinding allowance K by applying turning machining (boring machining) to the bore 10 of the cylinder 9, a process for forming a cut-in part 14 being deeper than the finish grinding allowance K on the surface of the bore 10 by applying turning machining to an oil groove forming part of the bore 10, and a process for grinding by only finish grinding allowance K by applying finish grinding (honing machining) on the whole surface of the bore 10 to form the oil groove 15 on the surface of the bore 10. When forming the cut-in part by turning machining, cut-in parts 14, 14 formed on the surface of the bore 10 by a turning tool 20 are not overlapped.