PURPOSE: To obtain an injection molding machine capable of cutting a gate without finishing work by installing a sprue bush, a gate cutting sleeve pin, a support plate, a sprue lock pin, etc. in special shapes.

CONSTITUTION: Retainer plates 1, 6 are adhered to each other, melted resin is stored fully in an cavity through a sprue bush 5, gatesealed and then, when a support plate 12 is pushed upward by a distance θ, a sleeve pin 9 is moved up to cut the gate 10a with the upper end of the pin and is inserted into the fitting hole 4 and the sprue 10b is departed from the upper end section of the sprue lock pin 15. As a result, the gate 10a and the sprue 10b are separated from the molded item 10c in the mold. Then, when the movable side is moved backward from the fixed side, the lower flange section 17a of a hang pin 17 approaches to the hole bottom 18a and touches it before long. When the movable side continues to move back, the flange section pushes up the support plate 13, the sprue lock pin 15 and the ejector pin 16 move up to project the sprue 10b and the molded item 10c out of the retainer plates 1, 6.