To provide an air conditioning method utilizing geothermal heat and its device capable of effectively utilizing geothermal heat in air conditioning by exchanging heat between the outdoor air and the indoor air.

This air conditioning method comprises a geothermal heat exchanging portion 1, a heat releasing portion 2 disposed inside the room, a circulating passage 3 for circulating a heat medium between the geothermal heat exchanging portion 1 and the heat releasing portion 2, and a heat exchanging/ventilating device 4, and the heat exchanging/ventilating device 4 comprises a first heat exchanging portion 9 exchanging heat between the outdoor air and the indoor air, and a second heat exchanging portion 10 exchanging heat between the outdoor air taken inside the room, and the geothermal heat, in taking the outdoor air into the room, and discharging the indoor air to the outside of the room.