To shorten a cycle time of a plastic injection molding machine to the utmost, on one hand, and to prevent collision of movable members, on the other.

The moving track of a first movable member of a plastic injection molding machine overlaps partially with the moving track of a second movable member. Based on an enabling signal showing the state of movement of the second movable member, the movement of the first movable member is started and one time scale is calculated on the occasion. A first time scale TWA and a second time scale TRAMAX are calculated and compared with each other. The first time scale TWA shows a time between the time point TFW of generation of the enabling signal and the time point t6 when the first movable member reaches the moving track of the second movable member, while the second time scale TRAMAX shows a time between the time point tFW of generation of the enabling signal and a time point t8 when the second movable member gets off the track of the first movable member. A moving passage 62 of the first movable member is controlled so that a difference between the two time scales be smaller than a prescribed minimum tolerance value ΔT2.