An apparatus for bending a workpiece comprises a stretching device for stretching the workpiece. In the process for bending the workpiece, an inclination angle made by a direction a tension force is acted to the workpiece and a direction a stretching forth is applied to the workpiece by the stretching member is detected. The tension force acted to the workpiece is controlled in such a manner that the stretching force from the stretching member is controlled in consideration of the inclination angle. Accordingly, the amount of the spring back after bending is uniform and an accuracy of the dimension of the bent workpiece is improved.
