To provide a facility capable of preheating and pre-cooling outdoor air treated by an air conditioner, at low cost.

An outdoor air preheating and pre-cooling facility is provided with an air conditioner 10 equipped with temperature conditioning means 12, 13 and a cooling tower 20 while the air conditioner 10 is constituted so as to guide outdoor air to the same, and a preheating and pre-cooling heat exchanger 15 is arranged at a position where the outdoor air is passed though before passing through the temperature conditioning means 12, 13. A circulation route 16 for circulating heat medium water through the preheating and per- cooling heat exchanger 15 and the cooling tower 20 is provided with a water sending means 17, while the circulation route 16 is provided with a heat exchanger 21 capable of heating the heat medium water through heat exchange between heat medium of a different system. Further, the circulation route 16 is provided with a bypass passage 31 for conducting the heat medium water to flow through the circulation route 16 while detouring the heat exchanger 21.