A backlight module (20) includes a light guide plate (21) and two light emitters (22). The light guide plate includes an emitting surface (212), a bottom surface (213) opposite to the emitting surface, a plurality of side surfaces interconnecting the emitting surface and bottom surface, and an incident surface (211) disposed at a corner portion thereof adjoining to two adjacent side surfaces. The light guide plate defines a through hole (23) in the corner portion adjacent to the incident surface. The two light emitters are adjacent to and face the incident surface.