Abstract: A heat exchanger for a vehicle engine includes a pair of tanks for supplying a coolant through a thermostat for adjusting opening/shutting depending on the temperature of the coolant and a water pump, and discharging the cooled coolant to an engine side; a header at one side coupled with the tank at one side, to which the coolant is supplied; heat exchange tubes which are structurally fastened to communicate with the heater at one end portion thereof, and arranged in parallel to a direction of driving wind; a header at the other side coupled with the tank at the other side, which is structurally fastened at the other end portion of the heat exchange tube to communicate therewith so as to discharge the coolant into the engine; and a core portion including fins fixedly brazed between the heat exchange tubes.