Abstract: A long length product is conveyed by a conveyor to a propulsion mechanism into contact therewith. The product is gripped by a first conveyor line vise and cut at its tailing end side into a specified dimension. The product is advanced by the propulsion mechanism against the conveying force of the conveyor and then gripped by the first conveyor line vise and machined. A series of these operations are iterated. Finally, the product is advanced to a second conveyor line side, where it is gripped by a second conveyor line vise and subjected to final machining with the propulsion mechanism retreated. Instead of using a process of cutting to cut the leading end side of the product to a specified dimension, the leading end side of the product may be put into contact with the stopper and fed by referencing the leading end of the product.