To provide a specific gravity separation method for molten incineration ash capable of certainly specific gravity-separating metals left in a molten slag only by melting the molten slag without mixing a molten slag layer and a metal layer separated by specific gravity again.

An induction heating coil 23 is installed on an outside of a recovery vessel 7 positioned at a periphery of the slag layer 21. A high frequency voltage is applied to the induction heating coil 23 and the molten slag is only induction-heated to a melting point or higher of iron 20 to melt the metal (iron, copper, etc.) left in the molten slag 21. The molten metal (iron, copper, etc.) is lamination-separated from the molten slag 21 to respective layers of iron 21 and copper 19 heated to a melting point or lower by specific gravity.