PURPOSE: To improve quality and stable operation by filling a mixture of particles of alkaline earth metal carbonates with alumina particles into the tap hole in a molten metal vessel.

CONSTITUTION: A filler for the tap hole in a molten metal vessel is produced by mixing 60-95wt.% particles of one or more kinds of alkaline earth metal carbonates selected from among limestone, magnesia and dolomite with 5-40wt.% alumina particles. The tap hole is closed and opened through a sliding nozzle. The filler is filled into the upper nozzle of the sliding nozzle for charging a molten metal fitted to a molten steel ladle, etc., to obtain a molten metal vessel with the set filler. A molten metal such as molten steel is received into the vessel and charged to a tundish for continuous casting, etc. The tap hole is easily opened.