A stacking-type, multi-flow, heat exchanger includes a plurality of heat transfer tubes and fins stacked alternately, and a pair of tanks provided at either end of the heat transfer tubes. One of the tanks has an inlet tank portion and an outlet tank portion for the introduction and the discharge of a heat exchange medium to the heat exchanger. The heat exchanger has a flange member connected to the one of the tanks, the flange member has a flange body, an inlet pipe communicating with the inlet tank portion and an outlet pipe communicating with the outlet tank portion, and at least one of the inlet and outlet pipes is formed separately from the flange body. A passage for introducing heat exchange medium from the inlet pipe to the inlet tank portion and a passage for discharging heat exchange medium from the outlet tank portion to the outlet pipe are arranged in a thickness direction of the heat exchanger in parallel to each other. In this structure, the heat exchanger may be made to be thinner, smaller, and lighter than known heat exchangers.