The present invention provides a light emitting diode, which comprises a first LED die and a second LED die, each die comprising a first semi-conductive layer, a second semi-conductive layer, and a multiple quantum well layer disposed between the first and the second semi-conductive layers, wherein the first semi-conductive layer of the first LED die is coupled to the second semi-conductive layer of the second LED die so as to form a serially connected structure whereby the consuming current and heat generation of the light emitting diode are lowered so that the size of heat dissipating device for the light emitting diode can be reduced and illumination of the light emitting diode can be enhanced.