A heat exchanger for realizing a high degree of humidity exchange efficiency at a low cost. The heat exchanger in which partition members respectively separated from each other by a spacing maintained by one of spacing members facilitate circulation of two different air flows, with total enthalpy heat exchange occurring between these two air flows via the partition members. The partition members comprise an air shielding sheet type material comprising a hydrophilic fiber and also including a moisture absorbent, and the air permeability (JIS P 8117) of the partition members is at least 200 seconds/100 cc.