A heat exchanging apparatus comprising: a case open upward; a heat exchange unit housed in the case ; and a storage tank arranged at an upper section of the case , wherein heat exchange fluid stored in the storage tank drops onto a heat transfer medium circulation pipe of the heat exchange unit by dead weight to exchange heat between the heat exchange fluid and a heat transfer medium, the heat transfer medium flowing through the heat transfer medium circulation pipe , wherein a heat transfer medium inlet and a heat transfer medium outlet are open in a same direction at both ends of the heat transfer medium circulation pipe , and a heat exchange fluid discharge port for discharging the heat exchange fluid having dropped in the case is formed on a side wall of the case either in the same direction as or in the opposite direction to an opening direction of the heat transfer medium inlet and the heat transfer medium outlet so that the heat exchange unit can be vertically taken in and out of the case , wherein the heat transfer medium circulation pipe is wound spirally along the vertical direction and wherein the heat exchanger unit comprises a rectangular frame for housing and holding the heat transfer medium circulation pipe , wherein the heat transfer medium inlet and the heat transfer medium outlet are open on one of fixing plates vertically installed to two opposite positions of the rectangular frame , and wherein a communication hole is formed on each of lower sections of both fixing plates so that either one of the communication holes communicates with the heat exchange fluid discharge port . a case open upward; a heat exchange unit housed in the case ; and a storage tank arranged at an upper section of the case , wherein heat exchange fluid stored in the storage tank drops onto a heat transfer medium circulation pipe of the heat exchange unit by dead weight to exchange heat between the heat exchange fluid and a heat transfer medium, the heat transfer medium flowing through the heat transfer medium circulation pipe , wherein a heat transfer medium inlet and a heat transfer medium outlet are open in a same direction at both ends of the heat transfer medium circulation pipe , and a heat exchange fluid discharge port for discharging the heat exchange fluid having dropped in the case is formed on a side wall of the case either in the same direction as or in the opposite direction to an opening direction of the heat transfer medium inlet and the heat transfer medium outlet so that the heat exchange unit can be vertically taken in and out of the case , wherein the heat transfer medium circulation pipe is wound spirally along the vertical direction and wherein the heat exchanger unit comprises a rectangular frame for housing and holding the heat transfer medium circulation pipe , wherein the heat transfer medium inlet and the heat transfer medium outlet are open on one of fixing plates vertically installed to two opposite positions of the rectangular frame , and wherein a communication hole is formed on each of lower sections of both fixing plates so that either one of the communication holes communicates with the heat exchange fluid discharge port . <EOS>