To surely determine a melting state of burned ash in a melting furnace and to properly control the melting state according to it.

The melting state control method for a burned ash melting device adapted to melt the burned ash AH in the melting furnace 1 provided with a heating electrode 11 and to granulate resulting molten slag with granulation water comprises: detecting the chlorine concentration of the granulation water by a chlorine concentration detector 71; and increasing the input power to the heating electrode 11 only in case that the chlorine concentration detected value exceeds a predetermined value.