Abstract: workpiece bending method and a workpiece bending apparatus that allow setting of a trajectory of a bending implement based upon a pre-processed shape of a workpiece and an intended post-processed shape of the workpiece. The workpiece bending method bends a flange of a workpiece via a processing roller, and includes a step for obtaining a pre-processed angle of the flange before processing and a flange length of the portion of the flange to be bent; a trajectory determination step for determining a path (trajectory) of the processing roller based upon the pre-processed angle, an intended angle after processing, and the flange length; and a processing step for moving the processing roller in a prescribed direction in accordance with the path determined in the trajectory determination step and then bending the flange until the intended angle is achieved.