Abstract: A molten-metal treating vessel is described having a lower section immersed in a bath of molten metal in a container so that the metal may be treated as desired while it is being partly introduced into and out of the treating vessel in a closed circuit, including a vessel body the lower section of which is open at the lower end, and an immersion drum removably attached to the upper peripheral edge to the lower opening edge of the vessel body and containing upward and downward flow passages. In the treatment vessel disclosed the ratio RS of the total cross sectional area (S.sub.1 +S.sub.2) of the upward and downward flow passages, which is the sum of the total cross sectional area S.sub.1 of the upward passages and that S.sub.2 of the downward passages, to the cross sectional area S of the opening at the lower end of the lower section of the vessel is not less than 0.3.