A hollow backlight module includes a first light guide plate, a second light guide plate, two light sources, a reflecting plate and a diffusing film. The first light guide plate and the second light guide plate form a hollow light-guiding zone therebetween. The two light sources are located respectively at two sides of the hollow light-guiding zone. The reflecting plate is located between the outer surface of the second light guide plate. The diffusing film is located above the outer surface of the first light guide plate. Lights emitted from the light sources first enter the hollow light-guiding zone and then into the first and the second light guide plates. The reflecting plate reflects the lights back to the hollow light-guiding zone. The diffusing film diffuses the light projected from the first light guide plate and outputs uniform lights.