To achieve a thermal power generating system with sea bottom hot water being applied as a heat source.

In order to suppress development cost and construction cost, the upper-most part of a power generating system major constituent element is set at a low depth from a sea surface or below and an entire system is moored at the sea bottom part, influence of tide power, ocean current and weather or the like over the power generation system is made minimum. Also, in order to suppress the cost, marine space down to the sea bottom is effectively utilized to constitute a steam generation and condensate system having a simple pipe structure. In order to make influence such as corrosion by salt contained in hot water minimum, hot water steam is not sent directly to a power generation turbine, but a heat exchanger is used to heat another thermal medium.