A backlight module includes a light source, a reflector, an optical fiber group, and a light guide unit. The light source emits light rays. The reflector defines a number of through holes. The optical fiber group includes a number of optical fibers corresponding to the through holes. Each of the optical fibers includes a first end and a second end opposite to the first end. The first ends of the optical fibers receive the light rays from the light source. The second ends of the optical fibers are inserted into the corresponding through holes. The light guide unit is positioned close to the second ends, receives the light rays from the second ends, and makes the received light rays distribute uniformly. The reflector reflects a portion of the light rays reflected by the light guide unit to the light guide unit again.