A plate processing device for use in a machine with a vertically acting ram; has a guide device mounted on the frame and a guide member which is pressed to a sliding surface of the ram. The guide member freely rotates around the centerline of the first vertical shaft and also freely rotates around the centerline of the second shaft perpendicular to the first shaft and parallel to the sliding surface and is constructed so that it follows the sliding surface of the ram. Also, a back gauge for the work is buffered against the shock of abutment with the workpiece and may be backed away from the workpiece. A pressing plate for the workpiece is supplied by a high pressure and a low pressure plunger, which are vertically actuated to provide a noiseless operation.