A Light Emitting Diode (LED) array module, which can be used as backlight, includes a bar-shaped Printed Circuit Board (PCB) on which conductive patterns for transmitting power are formed, a base formed on the PCB and made of a heat conductive material, a plurality of LED chips mounted on the base in a line and electrically connected to the conductive patterns of the PCB, a reflector formed to surround the plurality of the LED chips and adapted to reflect light radiated from the plurality of LED chips upward, and a lens formed above the plurality of LED chips and reflector to have a bar shape and adapted to diffuse the light radiated from the plurality of LED chips and reflector in a horizontal direction.