To reduce fuel for melting an ingot by disposing a suction blower in an exhaust gas duct extending between a melting furnace exhaust opening for introducing exhaust gas from a melting furnace to a preheater and the suction opening of the preheater thereby utilizing exhaust gas.

A pusher 3 is provided as a unit 3 for pushing and throwing a carried ingot A into a melting furnace. A preheater 4 is disposed on a roller conveyor 2 in order to heat insulate the ingot A carried on the conveyor 2 with exhaust gas from a melting furnace 1 until the ingot A is thrown into the melting furnace 1. An exhaust duct 6 provides a passage of exhaust gas storing thermal energy generated from the melting furnace 1. A suction blower 5 is coupled to the preheater side end of the exhaust duct 6. Since the ingot A can be preheated with exhaust energy from the melting furnace 1, the melting furnace 1 is simply required to generate heat for melting a preheated ingot.