To quickly and easily discharge hard slag which floats on molten metal in a ladle and is cooled and hardened, to out side of the ladle.

A slag dipping vessel 10 is surrounded with a bottom plate 11, both side plates 12, 12 and a back plate 13, and has an opening part 14 at the front part side confronting the back plate 13. This dipping vessel 10 is immersed in the slag S in the ladle L under state of inclining by raising the opening part 14, and after making the slag flow into the dipping vessel 10 from the opening part 14, the dig-up vessel 10 is raised and carried away.