To provide a slag-fuming method where, when a fuming furnace having an electric furnace type fusion section is used, the reduction in the temperature of a fused body accompanying the charge of a copper source to the fusion section is suppressed, and power consumption in the fuming furnace can be reduced.

The fuming furnace includes: an electric furnace type fusion section; a duct recovery section; and an exhaust gas duct section connecting the fusion section and the dust recovery section, and also satisfies the following requirements (1) and (2): (1), in the space of the exhaust gas duct section, zinc and lead volatilized from a fused body formed at the lower part of the fusion section is oxidized with the fed air, and, by oxidation heat generation accompanying the same, the temperature of an exhaust gas increases; and (2) the copper source is fed from a charge port provided at the outside of the fuming furnace to a chute for copper source charge installed in the space of the exhaust gas duct section, and while moving the inside of the chute, the copper source is preheated by the heating of the chute owing to an exhaust gas, and is thereafter exhausted from an exhaust port provided directly above the fused body in the fusion section.