To provide a waste incineration system which enables the design of a small-scale waste incineration equipment capable of performing incineration treatment of mixed waste, within the facilities, reduction of the amount of harmful substances in an incineration residue and an incineration flue gas, each formed in the waste incineration, and also effective utilization of waste heat.

The incineration process using this system comprises: subjecting mixed waste having various properties to pyrolysis in a pyrolysis equipment (incinerator) 1 having a heating region in an atmosphere having a low oxygen concentration or atmosphere containing no oxygen, to form a pyrolysis gas; introducing the pyrolysis gas into a reformer 4 for reforming the pyrolysis gas from the incinerator (pyrolysis equipment) 1 into a comparatively high grade fuel gas by using high temperature steam; combusting the fuel gas in a steam heater 10 for heating steam to a ≥700°C high temperature, to convert low temperature steam into high temperature steam and to continuously supply the high temperature steam to the reformer 4; and introducing a part of the high temperature steam or fuel gas into a secondary pyrolysis equipment 2, to subject a pyrolysis residue formed in the pyrolysis equipment 1 to secondary pyrolysis by using the high temperature steam, or secondary combustion by using the fuel gas. Thus, harmful substances in the mixed waste can be destroyed, decomposed and removed.