A waste-to-energy incineration system, in which the amount and heat value of exhaust gas largely changes in long and short periods, comprises an incinerator for burning waste, a boiler in the incinerator for generating steam with exhaust heat generated by the incinerator, a superheater for superheating steam generated in the boiler, a steam turbine driven by steam superheated by the superheater, a generator driven by the steam turbine, a fuel reformer for reforming source fuel, and a combustor burning fuel gas reformed by the fuel reformer and at least a part of exhaust gas led from the incinerator which is able to stably decompose generated dioxin in waste incineration exhaust gas.