PURPOSE: To obtain an endless metallic belt that is positioned stably at the center of the carrier groove of a V-shaped block by winding the endless metallic belt on two rollers having drum-shaped outer peripheral face, rotating one of them while shifting the rollers to separate them from each other and stretching the metallic belt to plastic region.

CONSTITUTION: An endless metallic belt 9j is wound on two rollers 19, 20 provided with drum-shaped outer peripheral faces having larger radius in the central part than that of side part and having spindles 21, 34 supported to allow rotation. The roller 20 is rotated, and at the same time, pressure oil is supplied to a hydraulic cylinder 28, and a tension support 25 is shifted to separate it from a supporting member 16. Consequently, the metallic belt 9j is stretched to plastic region, and the cross section of the metallic belt 9j is formed to convex shape.