PURPOSE: To prevent the accident of steel leakage from the joining part of a long nozzle by inputting a combustion heating material into a long nozzle with holding the lower end of the long nozzle dismounted from a changing ladle by dipping it in the molten metal of a tundish at the lower part and mounting a following ladle.

CONSTITUTION: At the stage of the residual steel in a ladle 1 becoming less the pressure fitting of the lower part nozzle of the ladle and a long nozzle 3 is released, the ladle 1 in an empty state is moved in the arrow mark direction and the change for the following ladle is performed. During the change, the long nozzle 3 is awaited with dipping the lower end and while under this standby a combustion heating material 4 is inputted into the long nozzle. As the combustion heating material 4, the paper pipe, wooden piece, etc., dissipating with combustion by the contact with a molten steel inside the long nozzle or by a radiant heat are used. The inputted combustion heating material 4 burns on the molten metal surface inside the long nozzle, preventing the solidification of the molten steel until the pressure fitting of the long nozzle 3 to the following ladle nozzle. Consequently, there is no skinning of the molten steel inside the long nozzle 3, so no nozzle clogging is caused and the pouring-in stream is flowed smoothly into a tundish 2.