A heat exchanger including first and second header tanks for receiving and discharging refrigerant. Further, the first and second header tanks are spaced apart from each other by a predetermined distance. Also include is a plurality of flat tubes each having opposite ends respectively connected to the first and second header tanks, in which each of the flat tubes has channels through which the refrigerant scatters and flows, and the channels have a different capacity from each other. Further included is a cooling member for discharging heat of the refrigerant flowing along the flat tubes.