An optical unit includes an optical element serving as a light guide path, which includes an incident entrance, an emitter, a light coupler which is arranged in the case where a plurality of incident entrances are arranged, and which couples a primary light, and a light separator which is arranged in the case where a plurality of emitters are arranged, and which separates the primary light to each of the emitters. The optical unit further includes a detector which directly or indirectly detects a leakage light leaking outside of the light guide path from the light guide path.