To solve the problems in the conventional repairing method for a tundish that the repair of the tundish is time-consuming work, or the manual work for dismounting and mounting an upper nozzle should be performed in a hot state.

A base plate is arranged between the bottom surface of the outer shell of a molten metal reservoir vessel and a slide type molten metal flow rate regulating device so as to be fixed to the bottom surface of the outer shell of the molten metal reservoir vessel after adjusting its position along the bottom surface. A through-hole is provided on the base plate so as to fit to the lower end of an upper nozzle, and the slide type molten metal flow rate regulating device is mounted on the base plate.