Abstract: A stroke-adjusting drive mechanism in which the stroke of a reciprocating member, such as a piston, is adjustable for use in machines such as hydraulic presses and press brakes is disclosed. The apparatus includes a cylinder and piston with a piston rod member which projects outwardly from the cylinder. A restricting valve means is arranged between a chamber of the cylinder defined by the piston member and a hydraulic passage connected with a hydraulic pump. An adjusting member is arranged in the piston rod member so as to be adjustably positioned along the axis thereof and a regulating valve is provided for restricting the flow of hydraulic fluid from the first chamber in response to changes of pressure and the hydraulic passage. By means of the apparatus of the present invention, the stroke length of the piston member can be easily and precisely adjusted as well as stopped at a desired position.