PURPOSE: To engrave a longitudinal groove toward the center of a wire material and make large-volume production by passing the wire material in the wire drawing die for longitudinal groove engraving provided with a protrusion from a die hole wall.

CONSTITUTION: A hole 3 is pierced in a die 2 molded of carbon steel, hard metal or the like and a protrusion 5 is installed from the wall surface 4 of the hole 3 toward the center of the hole 3. On the insertion side of the wire of the protrusion 5 is formed an edge 5' in order to ease the grooving of the wire and decrease the pass resistance of the wire. The shape of the protrusion 5 is V-form. A longitudinal groove is readily engraved in the wire material simply by passing the wire material in the wire drawing die 2 for longitudinal groove engraving. This not only makes large-volume production posible but also stabilizes quality.