PURPOSE: To obtain a clad ingot wherein the gradient of the concn. at the boundaries of dissimilar metals is continous and the dissimilar metals are surely joined by casting one kind of metal onto the bottom part of a mold in a nonoxidative atmosphere, allowing the same to solidify upward in one way and casting the next kind of metal thereon before the top surface of the former metal solidifies.

CONSTITUTION: While the inside of a mold 10 is held in a nonoxidative atmosphere by blowing gaseous Ar, one molten metal A out of two kinds of metal is charged through a lower inlet 141 for charging of molten metal. The metal A is cast up to a prescribed height and unidirectional solificiation is progressed upward from the bottom part. When the unsolidified part is only the top layer, the other kins of the molten metal B to be clad is cast through an upper inlet 142 for charging onto the molten metal A up to the prescribed height. As a result, the oxidation and interposition of foreign matter at the joining boundaries between the dissimilar metals, that is, A and B are completely prevented, and the surely joined surfaces at both surfaces are obtained. A layer of the components mixed with both metals is created at the above-described two boundaries, and the clad ingot wherein the gradient of the concn. of said components is continuous is obtained.