To provide a simply-constituted melting furnace saving energy and making NOx low.

The melting furnace 1 includes: a furnace body 2 for housing a material As to be melted; a burner 3 which can mix and burn fuel and main combustion air, so as to form a concentrated flame colliding with the material to be melted, and which can only partially burn the fuel by reducing a flow rate of the main combustion air; an auxiliary air nozzle 4 which supplies the inside of the furnace body 2 with supplemental combustion air for self-burning the fuel remaining in combustion gas after the fuel has been partially burnt by the burner 3; and a control means 10 which decreases the flow rate of the main combustion air of the burner 3 and increases the flow rate of the supplemental combustion air of the auxiliary air nozzle 4 when the material As to be melted is melted down.