PURPOSE: To simply prevent the eddy and the waving of molten metal and the staying of dross by floating up refractory floating bodies in the molten metal rotated while supplying fine bubbles and integrally fixing a hanging-down type baffle plate at the lower face thereof.

CONSTITUTION: In the molten metal 2 of aluminum, etc., incorporated in a treating vessel 3, an impeller arranged with blades 10 is rotated, and also, treating gas supplied from a gas supplying part 6 arranged in a rotary shaft 6 is injected from the opening holes arranged in the impeller 7. This treating gas is finely dispersed in the molten metal 2 by the rotating molten metal stream. In this treating device of the molten metal for removing dissolved gas and non-metallic inclusion in the molten metal, the refractory floating bodies 8 floated up in the molten metal 2 are arranged and the hanging-down type baffle plates 4 dipped in the molten metal 2 at the lower surface thereof are integrally fixed.