To supply outside air which has undergone heat exchange with geo-heat efficiently to two adjacent houses.

This air conditioning device 1 using geo-heat includes: a heat exchange part 5 for interconnecting first and second main pipes 2, 3 embedded in the ground approximately horizontally and in parallel by a plurality of branch pipes 4; introduction parts 6 each having one end communicated with the main pipe 2 or 3 and the other end communicated with outside air; and supply parts 7 each having one end communicated with the main pipe 2 or 3 and the other end communicated with inside of a building. The heat exchange part 5 includes; a buffer region B where no branch pipes 4 are provided between the adjacent houses H1, H2; and first and second heat exchange regions C1, C2 located on both sides of the buffer region B. The buffer region B includes: the introduction parts 6; the first supply part 7a for supplying outside air which has undergone heat exchange in the first heat exchange region C1 to the first house H1; and the second supply part 7b for supplying outside air which has undergone heat exchange in the second heat exchange region C2 to the second house H2.