A light guiding plate may include a substrate, a waveguide, and a reflective metal. The waveguide and the reflective metal may be formed on the substrate. The waveguide may guide light. The reflective metal may reflect the light guided along the waveguide to change a propagation direction of the light. A light guiding plate may include a substrate, a cladding layer, and a plurality of waveguides. The cladding layer may be formed on the substrate. The cladding layer may include a first insulating layer having a first refractive index. The plurality of waveguides may be formed on the cladding layer. The plurality of waveguides may include a second insulating layer having a second refractive index. The second refractive index may be higher than the first refractive index. The plurality of waveguides may guide light provided by a light emitting element. At least two of the waveguides may have different lengths.