A heat exchanger includes multiple tubes and multiple fins. Each of the tubes has a tubular shape extending in a horizontal direction. Each of the fins is disposed between adjacent ones of the tubes in a vertical direction vertical to the horizontal direction. Each of the fins is corrugated and includes bent portions located near the adjacent ones of the tubes and flat plate portions each of which extends in the vertical direction to connect between two of the bent portions. Each of the fins includes a pair of slits and an offset portion. At least a portion of the pair of slits extends to one of the bent portions. The offset portion is formed by having a portion of each of the fins between the pair of slits recessed inward of the one of the bent portions.