To provide a heat exchanger having a high heat exchange efficiency and also having a high heat exchange efficiency owing to the correlation between a spacing plate and partitioning plates.

The heat exchanger is structured so that partitioning plates 1 having a heat conducting and a moisture passing property are laid in layers one over another at a predetermined spacing while the spacing plate 2 in corrugated form is interposed, to allow the primary air stream and the secondary air stream to pass through between these layers alternately, whereby the temperatures and humidities possessed by the two air streams are exchanged continuously between the two streams through the partitioning plates 1, wherein the spacing plate 2 is furnished with a group of small holes 4 as a number of minute non-contacting structures in its part not contacting with the partitioning plates 1. Each partitioning plate 1 is furnished with a number of minute surface unevenness structures 3 in its part not contacting with the spacing plate 2.