PURPOSE: To improve the cleanliness of steam by introducing clean water into a transport pipe for the substance jetted from a separator in the forestage and allowing the contained components to be adsorbed into waterdroplets, in the captioned device equipped with plural stages of separators for separating the solid components in the substance jetted from a geothermal heat well.

CONSTITUTION: The captioned device is equipped with a well source separator 6 into which the substance (steam) jetted from a geothermal heat well is introduced through an introducing pipe 5, and the relatively rough components 7 are separated and removed outside the system. A separator 10 set before turbine into which the steam passing through the separator 6 is introduced through a transport steam pipe 8 is provided, and the finer constituents are separated and removed, and the steam which passes through the separator 10 is supplied into a turbine 13. In this case, the water whose temperature is lowered and passes through an introduced quantity adjusting valve 3 from a temperature lowered clean water injector device 1 can be introduced into the steam transport pipe 8, and the introducing quantity adjusting valve 3 is controlled by a controller 4 on the basis of the humid degree of the steam which is detected by a throttle calory meter 2.