PURPOSE: To produce an inorg. molded body enhancing strength and water resistance and capable of improving the workability of mold-setting etc., at the molding stage.

CONSTITUTION: An inorg. powder material is used as the raw material, to which alkali silicate and caustic soda as a binder and metallic silicon or its alloy as a hardening aid are added to deposit crystalline sodium silicate having 0.7-1.5 (SiO2)/(Na2O) molar ratio on the surface of the source material. Further, a specified water-resistant chemical and a reinforcing agent are added to the raw material to prepare a compounded sand. This compounded sand is poured into a die and hardened. As for the inorg. material, pearlite as an expanded body of pearlite or obsidian is used. The alkali silicate is sodium silicate or potassium silicate, and as for the hardening aid, metal silicon powder, mixture of metallic silicon and silicon dioxide, or ferrosilicon as an alloy of iron and metallic silicon is used.