PURPOSE: To reduce a rising time of extrusion by forming rugged stripes on the surface of an inner peripheral wall enclosing an extruded material circulating part behind a formed gap in the extruding direction.

CONSTITUTION: Rugged stripes 23a, 23b in the extruding direction are formed on the surface of the peripheral wall enclosing of a port 20 of a male die 12. Rugged stripes 28a, 28b in the extruding direction are formed on the surface of the inner peripheral wall of a recessed part 25 for forming a depositing room of a female die 13. The male die 12, the female die 13 are integrated into a conforming extruding machine and while supplying a wire, a wheel is driven rotatively to commence extrusion. The extruded material circulates along the rugged stripes 23a, 23b, 28a, 28b of the male die 12, the female die 13 toward the formed gap and much heat is generated by friction. Since the male die 12, the female die 13 absorb this heat, the temperature rises in a short period. The extruding speed can be improved and load to the extruding machine, too, can be reduced.