PURPOSE: To make effective use of dust containing carbon recovered from discharged gas outputted from a metallic scrap melting furnace and sludge containing aluminum produced when metallic aluminum is recovered from dross containing aluminum and save the fuel expenditure of the melting furnace.

CONSTITUTION: An auxiliary fuel injection nozzle 4 is arranged near a fuel injection burner 2 of a metallic scrap melting furnace 1. Auxiliary fuel comprising dust containing carbon recovered from discharged gas of the melting furnace 1 and/or sludge containing aluminum produced during a process in which metallic aluminum is recovered from the dross containing aluminum is blown from an auxiliary fuel injection nozzle 4 into the fuel injection burner 2 and then the auxiliary fuel is ignited together with fuel injected from the fuel injection burner 2.