PURPOSE: To execute a dewaxing stage and a drying and release agent-applying stage by using one pot with good workability, and to obtain a molding having high dimensional accuracy by using a specific heat source for dewaxing and polymerizing.

CONSTITUTION: A dental plate pattern 3 made of wax is fixed by gypsum 4 for fixing into a flask 1. A wax wire 6 for venting and a wax wire 7 for a wax sprue are provided in the side part of the dental plate pattern 3 and gypsum 8 for investment is admitted therein to embed the dental plate pattern 3 into the gypsum. The wax of the dental plate pattern 3 is melted and the melt is discharged from a bent port 5. The gypsum mold 22 is formed by dewaxing and the release agent is applied on the inside surface of the mold. A resin 24 is then press-fitted into the gypsum mold 22 and a flask 1 in the state of having a spring pressurizing device 32 is disposed upside down into a microwave oven 31. The microwave oven 24 is irradiated with microwaves. Consequently, the hydrous part 24a of the resin 24 is preferentially polymerized and cured first, then the non-hydrous part 24b of the resin 24 is polymerized and cured. The molding having the high dimensional accuracy is obtd. in this way.