PURPOSE: To make working time after molding unnecessary and shorten molding time, by a method wherein generated burrs are pressurized and cut by a deburring piece and a molded form, adhered to a male mold, is extracted by the up-and-down motion of the deburring piece and the injection of pressurized air.

CONSTITUTION: One set of separate molds, consisting of a male mold 1, fixed to a fixed platen 5, and a female mold 2, a clamped along a line X-X. A deburring piece 3, fitted to the male mold 1, is provided with a sharp edge 11 at the tip end thereof to cut burrs 12, produced on the peripheral surface of the shoulder of the male mold 1, upon clamping the molds by providing the deburring piece 3, connected to a hydraulic cylinder 7 arranged in the rear spacer 4 of the male mold 1, a rod 8 and a spring 10, with a predetermined pressure by the hydraulic cylinder 7. The deburring piece 3 is moved up-and-dowm simultaneously with the opening of a valve member 15, provided at the tip end of a valve rod 14 arranged at the center of the male mold 1, as the molds 1, 2 are opened and pressurized air is injected from a pressurizing chamber 13 toward the center of a cavity whereby a molded form 9, adhered to the male mold 1, may be released therefrom.