PURPOSE: To improve plant efficiency by way of preventing high temperature corrosion in a refuse incinerating boiler by heating a combustor by way of leading water or steam heated by a refuse incinerator to the combustor attached to a gas turbine in a combined power generation system including the refuse incinerator and the gas turbine.

CONSTITUTION: Gas generated in a refuse incinerator 3 is discharged from a chimney 6 through an exhaust gas processing device 5 after it is heat- exchanged by a refuse incinerating boiler 4. In the meantime, most of feedwater 18 boosted by a high pressure feedwater pump 17 becomes superheated steam 19 as it is led to a superheater 11 after it is heated by the refuse incinerating boiler 4 until it becomes saturated steam 25, and it is introduced to a steam turbine 20. At this time, a part of the feedwater 18 is heat-exchanged by an exhaust heat recovery boiler 15 and made to be the superheated steam 19, led to the steam turbine 20 with the superheated steam from the superheater 11 and it drives a power generator 13. Thereafter, the steam is condensed by a condenser 16. Additionally, the saturated steam 25 is introduced to the superheater 11 and made to be the superheated steam 19.