PURPOSE: To make possible smooth and sure extrusion without damage even in long use by communicating the material distributing hole of a male die with the extruding path of a female die and also freely attachably/detachably fixing the center parts of the male die and female die by joining means.

CONSTITUTION: In state where the material distributing hole 11 of the male die 10 is made to coincide with the recessed part 26 of the female die 20 and the contact surface 13 of the male die 10 and contact surface 25 of the female die 20 are worked together, the mutual outer edge parts of the male die 10 and female die 20 are connected with a pin and bolt. By inserting a bolt 30 with a hexagonal hole into the mounting hole 12 of the male die 10 and screwing into the tapped hole 28 of the female die 20, the male die 10 and female die 20 are tightly connected and fixed. Next, when aluminum as a material is distributed from the side of the material distributing hole 11 of the male die 10, after the material which is passed through the four material distributing holes 11 is joined in the recessed part 26 of the female die 20, conducted to the extruding path 21 and the main body of casing is extruded. Then, the main body is supported with the male die 10 through the bolt 30 with the hexagonal hole to the pressure that is applied to the center part 22 of the female die 20.