PURPOSE: To keep good condition fop the die clamping force at every cycle by adjusting the die clamping force at the next cycle under consideration of changing degree of the die clamping force in accordance with the changing degree of the die temp. during the former cycle, based on the die clamping force during the former cycle.

CONSTITUTION: At the first time of continuously forming, the die clamping force is adjusted at the desirable value, and the die clamping force is measured by a detecting instrument, built in the column 8. Whether this value is in the range of the standard value or not, is judged, and in case of being not in the range, it is readjusted to be in the range. Next, lubricant, etc., is supplied on the die and the die clamping is executed, and then the die clamping force FL1 and the die temp. just before injection start are started to measure, and after their confirmation, a series of operation is executed. And the die temp. for one cycle is measured and stored to operate rising degree of the all-round die temp. during the next cycle. Next, expansion and shrinkage of the die according to the changing degree of the temp., based on the die clamping force FL1 and the above-mentioned operating value, are found and then based on this value, rising degree of the all-round die clamping force during the next cycle is operated. Then, whether the max. die clamping force during the one cycle is in the permissible max. die clamping force of the forming machine or not, is judged.