To provide a machining method for a male screw which can efficiently machine a raw material having embedded reinforcing fiber in a male screw part, and causes no deterioration in strength of the male screw part.

A formed grinding wheel 5 is used for machining a trough part 1b of the male screw part on the raw material 3. The outer peripheral part of the formed grinding wheel 5 has the same shape of the cross section as the trough part 1b. The formed grinding wheel 5 is disposed so that an amount Δt of depth of cut relative to the raw material 3 becomes the depth of the trough part 1b. The formed grinding wheel 5 is rotated at a predetermined speed, and moved in the axial direction of the raw material 3 at a predetermined speed. The raw material 3 is rotated at the moving speed of the grinding wheel 5 and the speed corresponding to the pitch of the trough part 1b.