To ensure higher efficiency electric power generation by restricting to a minimum high temperature corrosion of a heat exchanger when the electric power is generated by gasifying solid waste.

A waste gasifying electric power generation apparatus is adapted such that it generates electric power by passing through a heat exchanger (overheater 50) combustion gas produced by combusting thermal decomposed gas obtained by thermally decomposing various wastes containing refuses and gasifying them and utilizing heat exchanged vapor. In the apparatus a fuel containing sulfur is introduced into a combustion furnace and combusted while bringing concentration of sulfur dioxide in the thermally decomposed gas to 200 ppm or more. The combustion is achieved with a burner 19 that combusts thermally decomposed gas for example. Thereupon, there is provided a monitor 61 for detecting the concentration of sulfur dioxide at a portion where the heat exchanger is provided, and the amount of supply of a sulfur containing fuel is controlled in response to a monitor output.