PURPOSE: To produce molds having thin and uniform refractory particle layers in casting surface parts by attracting a mixture of a binder resin and refractory particles electrically on the surface of a pattern, ramming the backing sand for molds thereon, curing said sand and separating the same from the pattern.

CONSTITUTION: A mold coating material prepd. by contg. a furan resin, sodium silicate, polyol, polyisocyanate, etc. as a binder, and mixing the same with fine powder of refractories such as zircon said, graphite, silica sand or the like is sprayed with a spray nozzle 2 on the surface of a pattern 1 for castings, whereby a thin layer 8 is formed. In this case, voltage is applied between the nozzle 2 and the pattern 1 to attract the negatively charged refractory materials electrically to the pattern connected positive to the earth. A molding flask 5 is set thereon, and molding sand mixed with a suitable binder is rammed therein as backing sand 6. After the refractory particle layer is cured by passing gaseous SO2, gaseous CO2 and gaseous amine respectively through the binders of the furan resin, sodium silicate, polyol, etc., the sand is drawed from the pattern 1, whereby a mold 7 is molded.