To provide a melting furnace which can stably melt an object to be melted regardless of the properties of the object.

A melting furnace which melts a treatment object supplied to a melting area 6 in the furnace and discharges the meet produced by melting through a slag hole 4 provided in the bottom section of the furnace is provided with a meltability discriminating means 20 which picks up an image of a discharged matter and discriminates the meltability of the treatment object from the picked-up image data and a treatment object supplying amount adjusting means which reduces the supplying amount of the object to a melting area 6 per unit time when it is discriminated that the object is less meltable than a standard object or, on the contrary, increases the supplying amount per unit time when it is discriminated that the object is more meltable than the standard object based on the meltability discriminated by means of the discriminating means 20.