Abstract: A sealing apparatus for shielding air from a path of molten steel in a laddle to a tundish in continuous metal casting facilities to prevent oxidation of the molten metal, the apparatus including a seal box lift mechanism mounted on a tundish body through a bracket and including a drive member and a lift rod member to be vertically moved up and down by the drive member; a seal box including an outer cylinder fixedly mounted on a tundish cover and extending into the tundish, and an inner cylinder telescopically fitted in the outer cylinder and connected to the lift rod member through a lever; a first seal member fixed at the upper end of the inner cylinder and pressed against a nozzle mounting surface of the laddle when the inner cylinder is lifted up by the lift rod member; a second seal member fixed on the outer cylinder to seal gap space between the outer and inner cylinders; and an inert gas inlet provided in the wall of the inner cylinder.