To provide a small underground heat sampling device with heat exchange pipes and a lifting pump into one unit.

The plurality of U-bent heat exchange pipes 2 are cylindrically combined, and the pipes each have one end connected to a circular liquid tank 3 on the upper part of the unit and the other end connected to the lower part of a pump chamber cylinder 5 extending downward through the center of the liquid tank. An air-lift pump 9 is stored in the pump chamber cylinder 5. The heat exchange pipes 2 are peripherally covered with a screen 11 and installed in a hole formed in a ground surface so that the heat exchange pipes 2 can be immersed in ground water 12.