PURPOSE: To make efficient mass production of a screw nail provided with a multithread screw on the outside circumferential surface in the shaft part by subjecting a shaft material having a sectional shape provided with short- and long-diameter parts to pressing and plastic deformation by divided press dies in such a way that the deformation in the long-diameter direction increases.

CONSTITUTION: A shaft material 11 having an elliptically shaped section provided with short- and long-diameter parts is inserted into press dies 12 and 12 divided to plurality and the material 11 is pressed by the dies 12, 12 to deform plastically said material. The resultant forming surfaces 13 are formed to the recessed shape coinciding with the outside diameter of a screw nail 1. The material 11 has the larger deformation in the long-diameter direction in this case and the projecting parts on the forming surfaces 13 of the dies 12, 12 are gnawed into the shaft 11. Drafts are made in the short-diameter direction and the recessed parts of the surfaces 13 by as much as said parts are gnawed. The material 11 is thoroughly pressed by both dies 12, 12 to form a screw 5 over the entire circumferential surface and detaining grooves 6 to the thread parts thereof. Both dies 12 and 12 are released after the press forming and the intended screw nail 1 is obtd.