To provide a method where organic substances in residue, sludge or the like containing useful metal components are made into an harmless state, so as to be easily removed, and further, the metal components in the residue, sludge or the like are separated and recovered at a low cost, so as to be made recycled as a metal.

Residue, sludge or the like containing rare or useful metal powder particles are recovered from a solution. The residue, sludge or the like are heated, are fed to a carbonization treatment apparatus, are indirectly heated in a heating cylinder, so as to be in a state of being baked in a casserole on an oxygen-free or oxygen-poor condition, and then heated and carbonized. Thus, organic substances in the residue, sludge or the like are heated, decomposed and gasified, are then introduced into a heating furnace, so as to be burned to be made harmless and then exhausted. Further, the metal component powder particles in the residue, sludge or the like are recovered in a state of being mingled with carbonized products of the organic substances. Thereafter, the carbonized products are heated and fed to a burning treatment apparatus to calmly burn only the carbonized components. In this way, the metal components are recovered in the state of oxide or in the state of non-oxide. The recovered metal components are separated by a means of dissolution, extraction or the like. Then, the metal components are smelted and refined, so as to be recycled as a metal.