To provide a melting method allowing the service life of the surface melting furnace of burnt ash, generated at the time of incinerating general wastes and industrial wastes to be improved rapidly.

At melting of burnt ash in a burnt ash melting furnace, provided with a mechanism supplying the burned ash to the upper part of an inclined hearth in the furnace from the outside of the furnace, a burner installed to the ceiling part of the furnace opposite to the inclined hearth surface for melting the burned ash and a sprue, which has a function of causing the melted burnt ash, flowing down the hearth surface from the upper part to the lower part to fall down to a cistern from the sprue, at the lower part of the inclined hearth surface, a thermite reacting agent is mixed with the burnt ash, and the angle of the inclined hearth is set at 10 to 30 degrees.