Abstract: A method of producing a composite steel body shaft by using at least one cooling metal mold having a cavity of a diameter and a steel body having another cavity of another diameter both of which cavities are coaxially disposed to define a through-hole in which the remelting and solidifying of electrode is effected to provide a shaft portion connected to the hollow body. At a contact position defined by both the metal mold and the hollow steel body at which contact position the diameter of the through-hole is reduced step-wise, a space is provided so that the diameter of the through hole is reduced gradually without the step-wise reduction of diameter of the through hole so as to prevent the confining of slag from occurring at the contact position.