Abstract: A light-emitting unit includes a substrate, an optical lens, and a light-emitting chip. The substrate has a surrounding groove and a retaining structure located in the surrounding groove. The optical lens is disposed on the substrate and has a concavity and an auxiliary retaining member, and the auxiliary retaining member has a retaining groove. The auxiliary retaining member is engaged in the surrounding groove, and the retaining structure is engaged in the retaining groove. The light-emitting chip is disposed on the substrate and located in the concavity. A reserved space is formed between the retaining structure and the retaining groove.