To provide a fluid exchanging system for recovering heat adapted for use in natural thermo carrier improved in its function.

This system comprises the natural thermo carrier 101, an automatic heat equalizing device 102, an automatic adjustment control body 103, an external passive exchanging fluid source 104, a transfer pipe 105, a main pump 106, a filtering device 108, a humidity adjusting device or a humidity treatment structure 109 and a control unit 110. In this system, the automatic heat equalizing device 102 and the fluid transfer pipe 105 are mounted in the natural thermo carrier 101, the fluid of low temperatures passed by the flow is heated by heat radiation, and the fluid of relatively high temperatures passed by the flow in the opposite direction, is cooled by heat absorption, thus the fluid is provided with a heat recovering function in a case of transferring the fluids in the directions opposite to each other.