PURPOSE: To always make the right and the left ends of a ram ascend and descend by the same height, by detecting an ascending/descending state of the vicinity of both the right and the left ends of the ram, by a pair of magnetic graduation scales, respectively, controlling the right and the left hydraulic operation devices, based on this detecting signal, and making the right and the left ends of the ram ascend and descend.

CONSTITUTION: The respective heights of both the right and the left ends of a ram 15 are detected by heads 27, 28 which have been connected to both the right and the left ends of the ram 15, respectively, and the right and the left magnetic graduation scales 25, 26 which have been connected to a frame 10 side. Based on a result of this detection, a supply of oil to the right and the left hydraulic operation devices 16, 17 is controlled, and the right and the left ends of the ram 15 are made to ascend and descend synchronously. In this way, the right and the left ends of the ram 15 can be made to ascend and descend by the same height. Accordingly, a control being suitable for a press work of an unbalanced load can be executed.