To provide a thermal power generation system capable of surely driving a turbine by a working medium of high pressure vapor even when the working medium is not sufficiently heated by a collector.

The working medium 3 is directly or indirectly heated by the collector 1 for absorbing heat energy, and the vapor of the working medium 3 is jetted from a nozzle 8, and the turbine 5 is rotatingly driven by the high pressure vapor from the nozzle 8. A generator rotor 6A in a generator 6 is rotated by rotation of the turbine 5, and electric power is generated by a generator stator part 6B oppositely arranged to the generator rotor 6A. A heating part 12 for reheating the working medium 3 is built in the vicinity of a nozzle inlet of a turbine unit 2 composed of the turbine 5, the generator 6 and a bearing 11 for supporting these turbine 5 and generator 6.