To eliminate the possibility of improper operation of a hydraulic cylinder and to safely and surely execute the changing work of a die from a holder by providing a front cover which is vertically moved by an elevating and lowering device and providing a switching lever for lifting and lowering a hydraulic cylinder and a switch with which the elevating and lowering means is operated only at inactive time of the hydraulic cylinder on both sides of the front cover.

The changeover switch 33 for operating a solenoid switching valve 32 is attached in the upper part before the right side of a fixed cover 27. The changeover switch 33 is electrically connected to a starting switch of a hydraulic pump 21 so as to be turned on only at inactive time of the hydraulic cylinder 17. After placing a die 4 in a prescribed position of the baseplate 12 of a press device 7 in the state where the front cover 28 is lifted and the hydraulic cylinder 17 is contracted, by operating a switching lever 24 by the left hand and the changeover switch 33 by the right hand, the front cover 28 and the piston rod 18 of the hydraulic cylinder 17 are lowered and the changing work of the die 5 from the holder 6 is safely executed.