PURPOSE: To prevent unremovable oxidizing scale of titanium and stainless steel from occurring by putting a ply metal on a parent steel material, putting a thin steel material on it, welding the circumference, sealing the internal part, performing hot rolling and forming a thin surface layer of steel material.

CONSTITUTION: A ply metal 2 of titanium and stainless steel is put on the surface of the parent steel material 1, the thin steel material 6 is put thereon, the circumference is welded 5, the internal part is sealed and hot rolling is performed. In this case, hot oxidized scale generated on the surface layer of a thin steel material 6 is removed in a pickling device for common steel material 6 to perform cold working. Thereafter, after a heat treatment carried out in the atmosphere, a thin layer of steel material on the hot oxidized scale and the ply metal is removed and then a slight cold treatment is executed. Then, it is possible to obtain clad steel having a homogeneous and nice surface of metallic luster and prescribed mechanical properties.