Abstract: The casting apparatus for a hollow steel ingot is constructed such that: at least three concentric pipes are provided in the central portion of an ordinary mold for a steel ingot; a core is formed by filling up a space formed between the first outer-most pipe having the largest diameter and the second pipe disposed inwardly of the first pipe with granular refractory material wherein zircon or chromite sand is bound by a binder such as an organic resin; a double pipe is disposed inwardly of said core and forming a gas flow course for cooling the core; and pouring gates formed through the stool for feeding molten steel at an intermediate portion between the inner wall of said mold and the core.