PURPOSE: To control freely motor torque and sense a foreign matter between molds with small clamping force not giving any damage to the molds by sensing a foreign matter between molds by means of a mold position sensing means and limiting the current value flowing to a servo-motor by a motor current limiting value putout means.

CONSTITUTION: A control device 5 drives a mold and a moving instruction is output to a moving instruction generating means 2 and also the current limiting value to limit the clamping force to the degree not to damage the mold to a motor current limiting value output means 10. Then, the action of a mold 6 balancing to the force equivalent to the clamping force and stopping is confirmed by a mold position sensing means 9, and the mold position at that time is sensed and compared with the allowance value L to some extent deducted from the molding position at the normal time preliminarily stored. If the present mold position is smaller than the value obtained by deducing from the mold position at the normal time preliminarily stored, it is determined that the balancing position is lowered because of a foreign matter between the molde and abnormality processing is carried out.