PURPOSE: To obtain a subject heat exchanger for cooling industrial gas which reduces an air leakage from a gap and promotes mixing with air at a fin side, by a method wherein a plate fin is formed in a rhomb or rectangle, and gaps in an air current direction between the adjacent plate fins are formed in a zigzag.

CONSTITUTION: An outer shape of a plate fin 3 is formed in a rhomb, and heat transfer tubes 4 are inserted thereinto to form a heat exchanging elements 6. The elements 6 are placed in a grid pattern and so that gaps between the elements 6 are formed in a zigzag. Thus, air, which leaks through the gaps in an air current direction between the heat exchanging elements 6, is increased in the flow resistance, whereby a leaked air can be reduced and a heat transfer efficiency can be improved. Furthermore, a leaked air from the gaps at the upstream side collapses with the heat exchanging element 6, and as a result, an air current is disordered. A heat transfer efficiency can thus be improved.