To provide an underground water heat exchange method and an underground water heat exchange device capable of preventing clogging in a well and maintaining the use of underground water heat and heat exchange performance for a long time.

The underground water in a casing 11 of a pumping well 1 is pumped up through a pumping pipe 14. While the underground water of which heat has been used is filled into a casing 21 of an injection well 2 through a return pipe 25, when the water level in the casing 21 of the injection well 2 is lifted to a preset water level, underground water in the casing 21 of the injection well 2 is pumped up through a pumping pipe 24 in the casing 21 of the injection well 2. The underground water of which heat has been used is returned to the inside of the casing 11 of the pumping well 1 through the return pipe 15. When the water level in the casing 11 of the pumping well 1 is lifted to a preset water level, the underground water in the casing 11 of the pumping well 1 is pumped up through the pumping pipe 14 again, and returned to the inside of the casing 21 of the injection well 2.