To provide a motor-operated mold opening/closing apparatus having a mounting constitution for simplifying a ball screw type feeding mechanism for advancing or retracting a movable die plate toward or from a fixed die plate, eliminating necessity of synchronously controlling a rotational speed and a rotational position of the ball screw shaft, and capable of absorbing an impact load without operating a contact on one side or a bending force in combination of the ball screw shaft and a ball screw nut.

The motor-operated mold opening/closing apparatus comprises a means for advancing or retracting the movable die plate toward or from the fixed die plate having a moving base including slide units mounted at both sides of a lower surface to mount the movable die plate on an upper surfacer, a pair of track rails laid on this apparatus base engaged with the slide unit to form a linear guide, the ball screw shaft supported in parallel with the rail via a bearing fixed to the base to be rotatably axially restricted, a servo motor for driving the ball screw shaft, and the ball screw nut engaged with the ball screw shaft and mounted on the lower surface of the base. The ball screw shaft and the ball screw nut are installed at arbitrary positions between the track rails of the pair of linear guides.