PURPOSE: To hold the air-tightness of a refractory tube member divided into at least two parts by improving the structure of a combined part integrally assembled, to restrain or prevent the generation of crack and breakage of the refractory tube in the operation of vacuum and pressurized casting and to enable the stable operation.

CONSTITUTION: The combination of both members 2, 3 in the combined part 4 consists of mutual screwing onto tapered screws 7 having 2-15° angle to the axis and in the range of 10-85mm pitch enabling the air-tightness. By this method, the service life of the refractory tube is drastically improved in the vacuum and pressurized casting for steel, and the casting efficiency and the safety can be improved and the casting cost is remarkably reduced and thus, extremely profitable effect is brought about. Further, as this result, the refractory tube for casting improves the reliability and profitability to the vacuum and pressurized casting.