To provide a method for starting a waste treatment facility for gasification and melting treatment of wastes, which can perform thermal compensation of a furnace body in a short time when starting the facility.

The waste treatment facility has a pyrolysis/carbonization furnace 4 for drying, thermal decomposition and carbonization of wastes, and a high temperature reactor 5 for partial oxidization/gasification and melting with oxygen containing gas of the carbonized products obtained in the pyrolysis/ carbonization furnace. In treating wastes using the waste treatment facility, the high temperature reactor is filled with carbon materials and the carbon materials are partially oxidized/gasified to raise temperature of the reactor in advance, or a mixture of the carbon materials and a gap filler for filling the gaps between the carbon materials, is subjected to heat treatment in the pyrolysis/carbonization furnace and the resultant heat treatment object is partially oxidized/gasified and melted in the high temperature reactor to raise temperature of the high temperature reactor in advance. Thereafter, the carbonized products of the wastes obtained in the pyrolysis/carbonization furnace are partially oxidized/gasified and melted.