A semiconductor light-emitting device includes a substrate having a base, a conductive layer and an insulating layer, a semiconductor light-emitting element and a resin member. The base has a pair of base first side surfaces and a pair of base third side surfaces. The conductive layer includes a front-surface segment and a side-surface segment. The front surface segment includes a front-surface first part. The insulating layer includes an insulating-layer first part and an insulating-layer second part. The resin member covers the insulating-layer first part and the insulating-layer second part of the insulating layer. A first thickness of the insulating-layer first part is greater than a second thickness of the insulating-layer second part.