The end portion processing apparatus includes an X-direction driving unit which allows a back-and-forth movement along an X-direction; a cutter supporting member which is supported by the X-direction driving unit, is able to run in a Y-direction, and supports a cutter member extending in a Z-direction which is perpendicular to the XY-plane; a guide member which has a shape matching to a processing planned shape when seeing from the Z-direction, and guides the cutter supporting member such that the cutter member moves to follow the processing planned shape; and a Y-direction position changing mechanism which changes the position in the Y-direction of the cutter supporting member to the work material. The Y-direction position changing mechanism changes the position of the cutter supporting member such that the cutter supporting member runs on further inner side in case of going back than in case of going forth.