A heat exchanger 100 has plate fins 1 laminated at an interval and a heat transfer pipe 2 inserted perpendicularly to the fins formed by a plurality of straight pipe portions 2s and a curved pipe portion 2r communicating end portions thereof with each other. In the plate fin 1, a first slit fin 3a protruding to the side of one face or the like and a second slit fin 3b protruding to the side of the other face or the like are formed by cutting and raising. A straight pipe portion 21a and the like are arranged in a zigzag state in parallel with each other, and a “step pitch Dp”, which is an interval between axial cores thereof in a step direction, and a “row pitch Lp”, which is an interval in a row direction, form relationships of “4 mm≦D≦6 mm, 14 mm≦Dp≦17 mm, 7 mm≦Lp≦10 mm” to an outer diameter D of the heat transfer pipe 2.