To obtain a method for eliminating loss when a plate fin tube type heat exchanger is employed in a spray type evaporation cooler and wetting the fins sufficiently while saving energy.

A plate fin tube type heat exchanger 1 is installed while inkcling such that the air speed is balanced with the gravitational speed of water flowing on the surface of fins 2. The fin 2 at the upper corner is bent at a predetermined angle such that the water 5 sprayed from an upper spray trough 4 does not leave the fin 2 at the upper end part to fly out of the heat exchanger but flows down along the edge of the fins without fail.