PURPOSE: To make the individual hydraulic pressure generating source needless and to reduce the cost and the setting area by providing the pressured oil supplying inlet with a switching valve from the oil pressure generating source and a return oil collecting inlet from a oil pressure operation system in the oil pressure operation system of a metal machine.

CONSTITUTION: In a press device 1, when a pressured oil supplying inlet 20 with a switching valve and a return oil collecting inlet 21 are installed on the side of a hydraulic unit 6, and the pressured oil of the hydraulic unit 6 provided in the press device is supplied to a chuck 12b of the metal machine 11 and a clamp, etc., an individual oil pressure generating source is made needless to be installed on the metal machine 11. Because the required pressure of the oil pressure operation system of the metal machine 11 is enough a low pressure comparing to the required pressure of the oil pressure operation system of the press device 1, a pressure reducing valve can be installed on the pressured oil tube from the oil pressure unit 6 to the pressured oil supplying inlet 20 with the switching valve. In such a way, the cost reduction and the reduction of setting area can be realized.