PURPOSE: To improve the workability at the time of exchanging dies by driving a motor for adjusting die height by the calculated shifting quantity of die thickness based on difference between the die thickness values for the new die and for the old die.

CONSTITUTION: An arithmetic control means 27 compares the inputted set die thickness value for the new die with the thickness value for the present die and the electrical motor 23 for adjusting die height is driven through driving circuit 34. Then, each tie-bar nut 6 is synchronously rotated, and a movable die plate 10 is shifted together with a supporting disc 3 based on measured information of the arithmetic calculation result and die thickness detecting sensor 26. Further, at the time when distance between a fixed die plate 2 and a movable die plate 10 becomes the value adding the prescribed allowance value to the die thickness for the new die, the electric motor 23 is stopped to complete the automatic die thickness shifting mode.