PURPOSE: To prevent the development of wrinkle at side face of a material to be rolled and to prevent seaming flaw by using a slab, which whole plate width direction is composed of only solidified structure at plate thickness direction, as cast slab for material to be rolled.

CONSTITUTION: For example, at the time of melting SUS 304 stainless steel by electric furnace and slab-making to the prescribed width, thickness and length, both end faces of plate thickness direction of mold are made to water- cooling metallic mold and both end faces of plate width direction is made to sand mold. Further, while heating the sand mold by burner, the slab-making is executed and the slab having only the solidified structure of plate thickness direction at whole plate width direction is produced. After heating, this slab at about 1200°C, the rolling of about 50% rolling reduction ratio is executed at live times, to make the plate having the prescribed thickness. By this method, the development of seaming flaw can be perfectly prevented, because of points of structure and crystal thereof.