To provide a device for positioning a workpiece in bending, in which positioning accuracy is improved by accurately positioning a workpiece having any shape of its butted surface, and further which has a simple structure, and to provide a method for using it.

A device 1 for positioning a workpiece in bending is provided with: a visible light projecting means 2, which are provided on back gage butting parts 10, 11 for positioning a workpiece W in the front and rear direction (Y axis direction) of metal dies P, D and a project visible light L as a reference line in the front and rear direction; and a reference position K, which is preliminarily set on the workpiece W so that the visible light L as a reference line passes through the position K when the workpiece W is positioned in the right and left direction (X axis direction) of the metal dies P, D.