To provide an ocean thermal energy conversion apparatus which can reduce a cost of the apparatus and stably give electric power without depending on ocean areas or seasons.

The ocean thermal energy conversion apparatus includes: a warm sea water pump that pumps up warm sea water from an ocean surface; a first heat exchanger phase-converting a liquid phase working fluid into a gas phase working fluid by heat exchange with warm sea water; a second heat exchanger converting warm sea water to cold sea water by heat exchange with an externally supplied cryogenic liquid; a turbine rotated and driven by the gas phase working fluid; a power generator axially coupled to the turbine; a third heat exchanger phase-converting the gas phase working fluid used for driving the turbine into a liquid phase working fluid by heat exchange with cold sea water; and a working fluid pump pressure-feeding the liquid phase working fluid obtained from the third heat exchanger to the first heat exchanger.