To provide a further effective geothermal heat using system by improving the heat-exchange performance of a heat exchange pipe buried in the ground with underground heat.

A swirling air flow generator 3 is set within the heat exchange pipe 4 to generate a swirling flow in the air sent from a blower 1 and carried in the heat exchange pipe. By spirally carrying the air in the heat exchange pipe 4, the contact distance of the air flow with the heat exchange pipe 4 is extended to increase the heat exchange quantity of the air flow with the heat exchange pipe. The air in a part close to the inner wall of the heat exchange pipe 4 is laid in a turbulent state to enhance the heat transmitting rate of the heat exchange pipe 4. Consequently, the heat exchange efficiency of the heat exchange pipe is improved to shorten the length of the heat exchange pipe, and the cost of the whole geothermal heat using system can be reduced.