PURPOSE: To produce the long-sized Mo foil having excellent deep drawing and flanging properties by expanding an Mo material in a transverse direction by using a pair of revolving rolls which are paralleled in axial centers in the longitudinal direction of the Mo material.

CONSTITUTION: The axial centers of a pair of the revolving rolls 2, 3 formed with roll body parts 2a, 3a as slopes along the axial centers are disposed in parallel with the longitudinal direction of the Mo material 1 to be rolled. While the both revolving rolls 2, 3 are kept rotated like arrows, the Mo material 1 is fed along the axial centers of the respective revolving rolls from ends 2b, 3b on one side of the revolving rolls where the inter-surface spacing is large. The Mo material 1 is rolled in the transverse direction and is expanded. The Mo material is delivered by the thickness of the spacing between the roll surfaces of the ends 2c, 3c. As a result, a bar material 4 is made into the state developed with the fibrous structures in the transverse direction orthogonal with the longitudinal direction thereof.