PURPOSE: To prevent generation of product defect by regulating contained hydrogen value in not more than the prescribed ppm value at the prescribed thickness range from a surface of a clad stainless steel plate.

CONSTITUTION: A mold 2 laid on a base plate 1 for a bottom casting arranges the stainless steel plate as the clad material 3 in an inside therein. Then, contained hydrogen value in the range of ≤10mm depth from the surface of the clad material 3 is regulated by ≤3ppm as the average. Next, after removing an oxidized film on the stainless steel plate 3, the steel plate 3 is spread by an oxidizing prevention agent 4 dissolved NH4BF4 powders in an organic solvent to form the clad casting ingot by the bottom casting for molten steel 5. As the average contained hydrogen value in the range of ≤10mm depth from the surface of the clad material 3 is regulated by ≤3ppm, adverse defects by ultrasonic test and generation of blisters at cold rolling for a rolling products are prevented. Therefore, in this way, the generation of defects in the products is prevented.