To provide a vertical fluid heat exchanger having a large heat exchange value and installed in a natural thermal storage body with high speed.

The vertical fluid heat exchanger including a first fluid inlet 701 and a second fluid outlet 702 is installed so that whole or part of the vertical fluid heat exchanger is mounted to the natural thermal storage body 1000 in vertical or downward oblique installation manner. Thermal conductive fluid made to flow outside is temporarily stored in a relay fluid storage drum 700, and a heat exchanger 705 is installed inside. A fluid pipe line for making thermal conductive fluid flow is installed in the heat exchanger 705. Thus, heat exchange is performed with the fluid within the relay fluid storage drum 700, and the fluid within the relay fluid storage drum 700 performs heat exchange with the natural thermal storage body 1000.