PURPOSE: To decrease considerably the amt. of inclusions without increasing the discharging speed of a molten steel by supplying the molten steel from a tundish to a mold side through a communicating pipe and adjusting the difference in the level of the molten steel between the inside of the tundish and the inside of the mold.

CONSTITUTION: When a molten metal is supplied from a ladle into a tundish 1, the level of the molten metal therein is detected and the difference Δh2 in the height between said level and the discharge hole of an immersion nozzle 5 is so adjusted that Δh2 attains a required value by a cylinder 10. A communicating pipe 6 is then lowered to install ends thereof in the tundish 1 and the mold 2. When the inside of the pipe 6 is evacuated with a vacuum pump 17, the molten metal 3 in the tundish 1 passes the inside of the pipe 6 and transfers to the mold 2 side, from which the molten metal flows through the nozzle 5 to the part 7 below the molten metal. The part 7 consists of a meltable pipe which melts when it contacts the molten metal 3. The evacuation is automatically ended by this melting and the molten steel is continuously supplied into the mold 2.