PURPOSE: To decrease the misalignment of both female and male dies and to manufacture the hollow material to be formed of a small amt. of thickness deviation with good yield by closely fitting the annular restricting member to the outer peripheral part of the male die body in the state of operating the pressurizing force directed to inward radius direction to the male die body.

CONSTITUTION: When the cylindrical material to be formed 21 is extruded by using the die 3 for extrusion, the pressurizing force directed outward the radius direction is operated at the inner peripheral surface of the male body 9 and operates so as to expand the male die body 9, due to the billet metal 22 passing through the metal passing part 13 between the bridge parts 10... of the male die 6. On the other hand, the expanding deformation of the male die body 9 is prevented by operating the pressure directed inward the radius direction with the restricting member 18 on the male die body 9. Therefore, the generation of misalignment of the male die 6 and the female die 7 in the die ring 4 during extrusion is prevented, and the thickness deviation for the material to be formed 21 is decreased.