To obtain a hollow die for extrusion having an internal cross-section dimension with a small error.

A male mold 2 is provided with a mandrel 8 which is protrusively formed and has a male side bearing part 10 of a shape corresponding to the inner circumference of a hollow shape material. A female mold 4 is provided with a female side bearing part 24 of a shape corresponding to the outer circumference of the hollow shape material. A molding clearance 30 is formed by combining the male mold 2 and the female mold 4 to insert the male side bearing part 10 into the female side bearing part 24. The relation between the length L of the mandrel 8 and the cross-sectional area S of the mandrel 8 is set to be 0.02 < L2/S < 2.0. When forming a hollow shape material by extruding a billet through the molding clearance 30, the deflection of the mandrel 8 is reduced.