To provide a method for manufacturing a forming body with a groove for forming the oblique surface of the groove with excellent surface roughness and easily changing an angle of the oblique surface of the groove.

By rotating a workpiece W and making a tip 11 abut on the outer peripheral surface 4, the groove 5A of a prescribed angle α corresponding to an outer edge shape of the tip 11 is formed. Subsequently, the tip 11 is relatively inclined to the workpiece W by changing a height position of the tip 11 to form the groove 5B having an angle α' larger than that of the groove 5A.