PURPOSE: To obtain a rational and economical heat exchanger which has excellent heat exchanging efficiency, a small size, energy conservation and low noise by skillfully utilizing the evaporation of water.

CONSTITUTION: A heat exchanger has tubes 5 having fins 3 and arranged in a trombone state to cool refrigerant flowing through the tubes, and comprises water distribution pipes 9 disposed in parallel with the upper sides of substantially horizontal tubes and having a plurality of water discharge holes 17 for uniformly supplying water to the outer surfaces of the fins 3 and the tubes 5, and water transmission means 13 for feeding water into the pipes 9, wherein the supply of the water from the holes 17 of the pipes 9 is limited to the small quantity of the degree for expediting the evaporation of the water from the outer surfaces of the fins 3 and the tubes 5.