A semiconductor light emitting device (A) includes an elongated substrate (1) formed with a through-hole (11), a first, a second and a third semiconductor light emitting elements (3R, 3G, 3B) mounted on the main surface of the substrate (1), and an electrode (2R) electrically connected to the first semiconductor light emitting element (3R) and extending to the reverse surface of the substrate (1) via the through-hole (11). The first semiconductor light emitting element (3R) and the through-hole (11) are positioned between the second semiconductor light emitting element (3G) and the third semiconductor light emitting element (3B) in the longitudinal direction of the substrate (1). The second semiconductor light emitting element (3G) is arranged closer to one end of the substrate (1), whereas the third semiconductor light emitting element (3B) is arranged closer to the other end of the substrate (1).