A light emitting module includes a light source, a light guide plate, and a reflecting mask. The light source includes a circuit board and a light emitting device fixed on the circuit board. The light emitting device includes a plurality of light emitting elements and a control circuit. The light guide plate receives light from the light emitting device and exits from the light guide plate, includes a plurality of light emitting sidewalls, a plurality of reflection walls, and a receiving hole defined in the light guide plate. The receiving hole includes a plurality of light incident sidewalls. The reflecting mask covers the receiving hole, including a bottom surface and a plurality of reflecting surfaces.