The invention provides a sand mixing device for casting. The sand mixing device comprises a machine box body, a sand mixing bin, a feeding device and a driving system, wherein the driving system is arranged at the bottom of the machine box body, and the sand mixing bin and the machine box body are connected through the feeding device; and a filtering layer is arranged in the machine box body and divides the machine box body into a stirring cavity A and a stirring cavity B; the stirring cavity A serves as a rough stirring area, the stirring cavity B serves as a fine stirring area, and the mixing uniformity is improved through stirring by areas; and the stirring cavity A is in a funnel shape, the stirring cavity B is cylindrical, and the central axis of the stirring cavity A is perpendicular to the central axis of the stirring cavity B. According to the design purpose, the sand mixing device can conveniently move and be filled with sand through the driving device, no large-scale sand conveying and casting equipment is needed to be arranged in a workshop, and therefore the equipment cost can be reduced, and the sand mixing uniformity can be improved by stirring equipment; and meanwhile, the sand mixing device has the advantages that the sand can be fed and mixed continuously, and therefore the efficiency of casting and mixing the sand can be effectively improved.