A heat exchanger includes a heat exchange core including a plurality of heat exchange tubes, a refrigerant inlet header and a refrigerant outlet header arranged toward one end of each heat exchange tube, and a refrigerant inflow header and a refrigerant outflow header arranged toward the other end of each heat exchange tube. The outlet header has an interior divided into two spaces by a flow dividing resistance plate, and some of the heat exchange tubes are joined to the outlet header so as to communicate with the space. The resistance plate has a plurality of refrigerant passing holes formed therein that are different in shape and/or size. The outlet header is provided on the outer surface thereof with identification marks for discriminating the positions of the refrigerant passing holes and representing the shapes and/or sizes of the holes.