To improve the draining ability of an air heat exchanger provided with flat perforated heat transfer tubes and corrugated fins.

This air heat exchanger is provided with flat perforated heat transfer tubes 1, 1,... each having a plurality of refrigerant flowing holes 2, 2,... inside and the tubes 1, 1,... are vertically arranged in parallel. In addition, corrugated fins are brazed among the tubes 1, 1,.... In this case, drainage ditches 3 having depths which are about 1/2 of the thicknesses of the tubes 1, 1,... are provided on the surfaces of the tubes 1, 1,... not corresponding to either one or both of the flat heat transfer surfaces 1a and 1b of the tubes 1, 1,... which become the brazing surfaces for the corrugated fins.