In a heat exchanger comprising a plurality of plates arranged adjacent to each other and provided with turbulence-generating corrugations, sealed passages for two heat exchanging media are enclosed between the plates, and two heat exchanging media flow through the passages in mutually inclined flow directions. In order to provide different thermal properties of the passages for the two media, the corrugations on an average extend at a wider angle relative to the flow direction of one of the media than to that of the other medium.