PURPOSE: To make the smooth controlling of mold opening and closing process possible by a structure wherein computing means, which computes the manipulated variable in mold opening and closing process by performing fuzzy logic operation on the basis of the information obtained from setting means, which sets mold opening and closing positions, and detecting means, which detects mold opening and closing states, and controlling rules brought from memorizing means.

CONSTITUTION: On the basis of set values and detection values respectively inputted at all times from a position setter 10 and a state detector 11 to an arithmetic unit 12, total stroke (t), remaining stroke (s) and mold opening and closing speed (r) are outputted to a fuzzy inference section 7 in the arithmetic unit 12. In the fuzzy inference section 7, controlling rules R1, R2, R3... stored in advance in a memory 8 are fetched so as to compute manipulated variable (c) by fuzzy inference on the basis of the controlling rules in order to output the variable to the controlling device 9 of mold opening and closing, which controls the actions of an injection molder in mold opening and closing process in response to the manipulated variable (C).