In order to provide a functional air conditioner that can perform advanced sterilization and purification of air in various facilities such as offices and factories as well as ordinary houses, and provide a safe, comfortable and healthy living space. The air A in the room R or the outdoor S is sucked from the suction port Pa, sent to the underground G, the air A is heat-exchanged in the ground G, and the heat-exchanged air A is discharged into the room R from the outlet Pb. A geothermal heat-use functional air conditioner equipped with a feed pipe P. The feed pipe P includes a forward path 11 for sending air A from the ground to the ground, and underground heat in the ground. A reciprocating pipe section 10 having a return path section 12 for returning the heat-exchanged air A to the ground, and having a disinfecting liquid W stored between the outlet Pb and the ground exhaust opening 10b of the reciprocating pipe 10 A vessel 2 is interposed.一般住宅はおろか、オフィスや工場等の各種の施設に於て、空気の高度な殺菌・清浄化が行なえ、安全で快適かつ健康的な生活空間が得られる機能性空調装置を提供するために、室内Ｒ又は室外Ｓの空気Ａを吸入口Ｐａから吸い込んで、地中Ｇに送って、地中Ｇにて空気Ａを熱交換させ、熱交換した空気Ａを室内Ｒに吹出口Ｐｂから排出する送流配管Ｐを備えた地中熱利用の機能性空調装置であって、送流配管Ｐは、空気Ａを地上から地中に送るための往路部11と、地中にて地中熱と熱交換された空気Ａを地上に戻す復路部12と、を有する往復管部10を備え、吹出口Ｐｂと、往復管10の地上排気口10ｂの間に、消毒液Ｗが貯えられた殺菌清浄器２を介設している。
