A semiconductor light-emitting device 10 includes a heat sink and a semiconductor light-emitting element mounted on the heat sink. A gap is provided between a region of a part of a base bottom surface of a base of the semiconductor light-emitting element and an upper surface of the heat sink, and a lead is disposed in a region where the gap is provided so as to vertically pass through the base. A semiconductor laser chip is provided in a region where the gap is not provided so that its waveguide longitudinal direction is substantially parallel to an upper surface of the base. The lead has its lower end located within the gap and connected to a flexible substrate.