A backlight module includes a light guide plate, a reflecting unit, two light emitting units, and two light absorbing units. The light guide plate has a first surface, a second surface opposite to the first surface, and two light incident surfaces connecting the first surface and the second surface. The two light incident surfaces are respectively located at two adjacent corners of the light guide plate. The reflecting unit is disposed on the second surface. The two light emitting units are respectively disposed beside the two light incident surfaces. Light beams emitted by the two light emitting units are capable of entering the light guide plate respectively through the two light incident surfaces and being transmitted out of the light guide plate through the first surface. The light absorbing units are disposed between the second surface and the reflecting unit and are respectively adjacent to the two light incident surfaces.