To increase generation efficiency through low-cost and simple constitution and realize gasification power generation even by fuel having low and stable NOx in exhaust gas.

A gasification power generating system comprises a gasifying means 10 to generate high temperature gasification generation gas by reacting fuel 17 and a gasifying agent 16 with each other; a generating means 20 to effect power generation by using energy generated by burning high temperature gasification generation gas generated by the gasification means 10; and a preheat means 30 to preheat the gasifying agent, fed to the gasifying means 10, to a self-ignition temperature, for example, approximate 1000°C. The preheat means 30 increases a temperature of air fed in the gasifying means 10 to a high temperature of approximate 1000°C when, for example, fossil fuel such as coal is used as the fuel 17.