PURPOSE: To execute working with high accuracy by lowering a slide which is guided on a slide guide down to a bottom dead point and mounting an upper die to the slide after at least either of the horizontal positioning of the slide or the horizontal positioning of the upper die is executed.

CONSTITUTION: A hydraulic oil is supplied to a hydraulic chamber 28 of the 1st device and a guide bushing 17 is thereby bulged and deformed in its inside diameter direction to decrease the clearance with a guide post 15 to zero. At least either of the slide 10 and the upper die 20 is horizontally positioned when at least either of the slide 10 and the upper die 20 is horizontally positioned and the respective cylinders of the 2nd and 3rd devices are behaved to elongate. The upper die is mounted to the slide after the above-mentioned positioning. Since the upper die mounting operation is executed in the positioned state in this way, the upper die is positioned exactly with respect to a lower and since the pressing of a material is executed in the state of maintaining this positional relation, the high-accuracy working is attained.