A backlight module includes a light guide plate and two light emitting elements for emitting light beams. The light guide plate includes first and second light guide portions and a connecting portion interconnecting the first and second light guide portions. The first light guide portion has two opposite first light incident surfaces at opposite sides thereof, and a first light output surface. The second light guide portion has a second light incident surface facing first light output surface of the first light guide portion. Each of the light emitting elements faces one of the first light incident surfaces of the first guide portion. The first guide portion receives the light beams via the first light incident surfaces and output them via the first light output surface. The second light guide portion receives the light beams from the first light output surface via the second light incident surface.