Abstract: A semiconductor light-emitting device includes a lead frame, a light-emitting element, and a reflection layer. The lead frame includes a main body and a side body extending upwardly from the main body. The main body and the side body cooperatively define a receiving space. The side body has an inner surface facing the receiving space, and a first height measured from a surface of the main body. The light-emitting element is disposed on the surface of the main body and in the receiving space. The reflection layer covers at least a part of the inner surface, and has a second height measured from the surface of the main body. The second height is not smaller than 90% of the first height.