A heat exchanger that can prevent damage to joints of tubes and side plates at core plates and is easy to produce which has side plates enabling stable brazing of the tubes and fins with the side plates, that is, a heat exchanger provided with a plurality of tubes through a heat exchange medium passes, a plurality of fins alternately stacked with the tubes and increasing the heat transfer of the heat exchange medium, core plates to which the two ends of the tubes are connected, and side plates arranged at the outsides in the stacking direction from the end fins arranged at the outermost sides in the stacking direction of the fins and connected to the core plates, wherein at least one of the side plates has a plurality of bridge portions at intermediate locations in the longitudinal direction, and at least one location of the bridge portions has a slit provided by cutting after the brazing of the tubes and the fins.