Abstract: An object is to provide a mold molding method which can provide a high general-purpose property and can reduce a usage quantity of molding sand. In a method for molding a mold (sand mold) by self-hardening molding sand using a caking additive, the mold is molded by disposing hollow spheres each formed to have no clearance therein among molding sand mixed with the caking additive. Preferably, the hollow sphere may be formed by working two metal plates to semispherical shapes and then connecting the semispherical-shaped metal plates to each other by welding their respective whole peripheries. A specific gravity of the hollow sphere may be 0.5 to 2.0 times a specific gravity of the molding sand.