To provide a geothermal unit efficiently operable and capable of reducing cost by improving workability.

A soil heat exchanger 2 is connected to a heat pump 3 through a primary cooling medium pipe arrangement 5, and heat is supplied to the side of an air-conditioning indoor machine 4 from a natural cooling medium in the primary cooling medium pipe arrangement 5 through a primary condensation/evaporation unit 9 or heat is absorbed by the natural cooling medium in the primary cooling medium pipe arrangement 5 from the air-conditioning indoor machine 4 side, whereby energy required for circulation can be reduced as compared with the case where heat medium water is circulated by a circulation pump on the primary side and energy efficiency of a whole air-conditioning device 1 can sufficiently be increased. In addition, by connecting the soil heat exchanger 2 to the heat pump 3 through the primary cooling medium pipe arrangement 5, workability of the pipe arrangement can be improved and the installation cost thereof can be reduced.