PURPOSE: To mold release a molded product surely, cutting and removing the final of a sprue by cooling and hardening the final end of the sprue by means of feeding air to the nozzle part of a cylinder, immediately after the cylinder has been retracted after injection molding.

CONSTITUTION: While clamping a movable mold 5 to a stationary mold 4, the nozzle 2 on a cylinder 1-tip is caused to be in contact with the injection port of the mold 4. Molten resin kept in the cylinder 1 is poured into the mold cavity and a product 6 (numeral 7 is its sprue) is molded. Next, immediately after the cylinder 1 has been retracted, air is supplied from an air pipe 9 to the final end 8 of the sprue by which the mold 4 is connected with the tip of the nozzle 2 in filamentous state thereby causing it to be hard by cooling and to be brittle. Next, when the movable mold 5 has been retracted, the sprue and its final end 8 are cut off under their own weight and drop outside of the stationary mold 4. Then the molded product to which the sprue 7 is stuck, drops inbetween the mold 4 and 5 and is recovered.