Abstract: In a continuous casting a hollow ingot by means of a forcedly cooled tubular mold and a core, gas is introduced around an outer peripheral surface of the core along longitudinal slits to form an annular gap surrounding an inner peripheral surface of hollow metallic molten metal, and gas pressure is applied on said inner peripheral surface of the hollow molten metal. Refractory heat-insulative material, starter bar, is brought into contact with the molten metal poured into said annular space at the casting start, encased in the metal solidified thereon, and withdrawn together with the hollow ingot being withdrawn. By these methods smooth cast skin is formed on the inner peripheral surface of a hollow ingot.