According to the invention, by setting the linear thermal expansion amount when a mold made of a molding sand is heated from a room temperature to 1000° C. to be not more than 0.9%, and the ratio (D/d) between the diameter of a slump (D) and the diameter of a slump cone (d) in a slump test of the molding sand having a hardening agent kneaded to be not less than 1.65, a molding sand preferable for use in a mold produced using the self-hardening type of three dimensional laminate molding sand mold, having low thermal expansibility preventing occurrence of a veining defect, and capable of forming a large and complicated shape can be obtained.