PURPOSE: To prevent the breakdown of frozen crust and reduce the occurrence of accidents during casting by applying the compressive force complying with the compression quantity equivalent to the bloom shrinkage quantity to the bloom during bloom stop time.

CONSTITUTION: A tundish 1 and push mechanism 5 are connected by means of a connecting rod 4. The push mechanism 5 is beforehand so set that push operation is accomplished during the stop time of a bloom 12 and that pull operation is accomplished during the drawing time, to apply the compressive force complying with the compression quantity equivalent approximately to the shrinkage quantity of the bloom 12 to the bloom 12 from the tundish 1 side. This lets the thin portions of the frozen crust formed on the surface of the molten steel be reinforced at the connecting step part of the tundish nozzle 1 and casting mold 7 and improves the quality of the bloom 12.