PURPOSE: To utilize the heat energy of terrestrial heat water, which is thrown waste according to conventional turbine with vanes, efficiently by introducing the terrestrial heat water to a screw type two-phase stream expanding machine and by generating electricity through utilization of this heat energy.

CONSTITUTION: The terrestrial heat water and the mixture of hot water and steam from a steam jetting well 1 shall flow into an air/liquid separator 3 from a conduit 2, and the steam is led to the turbine generating part through a pipe 4. Meanwhile the hot water is sent to a screw type two-phase stream expanding machine 9 pasing through a divergent pipe 7 and an regulator valve 8 from a hot water leadout pipe 6 under regulation of a level meter 5 and, after generation of electricity by turning a geneator 10, flows out from an exhaust pipe 11 to be introduced into a separator 12.