Abstract: Provided is a straightening press for a rod-like workpiece which is supported on a carrier sliding on a stationary base table. A plurality of detection units are disposed at intervals along the longitudinal direction of the workpiece. Each detection unit is provided with a sliding member sliding between the detection position for permitting a sensing element to contact the outer periphery of the workpiece and the retirement position for permitting said sensing element to be released from contact with said outer periphery, and said sensing element is provided on one end portion of a lever rockably supported by said sliding member, and the operating plunger of a differential transformer engages the other end portion of said lever.