A heat exchanger for a vehicle may include a heat radiating device and a valve device. The heat radiating device includes a plurality of inflow holes and a plurality of discharge holes that are thinned at a side of the heat radiating device, allows respective working fluids to flow into and to be discharged therefrom, includes flow paths that are alternately formed by stacking a plurality of plates so that the respective working fluids flow in the flow paths, and exchanges heat between the working fluids that flow through the respective flow paths. The valve device is connected to the respective inflow holes and one of the discharge holes, and allows one of the working fluids to flow into the flow path or bypasses the one working fluid to control the flow of the working fluid by using linear displacement which changes in accordance with temperatures of the respective inflow working fluids.