PURPOSE: To work safely and accurately a material to be worked by approaching a punch and a die to a safe distance between the same by a both-hand operation in the stage of starting an operation then stopping automatically the movement and approaching the punch and the die further after detecting the disposition of the material between the punch and the die.

CONSTITUTION: The operator operates a both-hand push button device 5 to approach a die 19 to a punch 29 to a safe distance and immediately when the ram of a hydraulic press arrives at the safe region, a command for stopping the ram ascent is emitted to stop the ram. When the ram is moved upward, a material 65 to be worked is butted to all of the plural detectors 69 of a back gage device 21 to turn on an automatic contact signal. A numerical control device 3 reads the distance between the material 65 atop which the punch 29 is pressed and the die 19 as much as to make the material 65 immobile, then the device moves upward the ram. Whether the lower limit setting of the ram is performed or not is judged and the ram is stopped at the lowermost limit, by which the working of the material 65 is completed.