PURPOSE: To carry out a stabilized continuous molding without generating defective molding or damaging a mold by minimizing the impact to a mating surface of a fixed side mold and that of a movable side mold in the case of molding a precision molded product, for example, an optical disk.

CONSTITUTION: The deviation amount of movement of a fixed side platen 5 and a movable side platen 4 is measured at the time of every molding operation of a continuous injection molding, and the deviation amount is compared with the reference value, and in the case the deviation amount is beyond the reference value, the molding is discontinued.