A semiconductor light-emitting device includes a lead frame, a semiconductor light-emitting element mounted on the top surface of the bonding region, and a case covering part of the lead frame. The bottom surface of the bonding region is exposed to the outside of the case. The lead frame includes a thin extension extending from the bonding region and having a top surface which is flush with the top surface of the bonding region. The thin extension has a bottom surface which is offset from the bottom surface of the bonding region toward the top surface of the bonding region.