[Problem to be solved] To achieve a reduction in facility costs in a geothermal power-generation system.[Solution] To provide a compressor 11 that compresses air, a heating device 14 that heats compressed air compressed by the compressor 11 by geothermal heat, a turbine 12 that obtains a rotational force by heated compressed air heated by the heating device 14, and a generator 13 that generates power by the rotational force inputted from the turbine 12.