In a III group nitride compound semiconductor wherein light that has been emitted in a light emitting portion formative layer is reflected by a multilayered reflection layer that is provided between the light emitting portion formative layer and sapphire substrate, it is desirable, for increasing the reflection efficiency of the light that has been emitted in the light emitting portion formative layer, that the multilayered reflection layer be provided at a position that is as near to the light emitting portion as possible. However, since the multilayered reflection layer is high in resistance value and also high in power consumption, locating the multilayered reflection layer near the light emitting portion formative layer results in that the resistance value in the vicinity of a relevant cathode electrode becomes increased. This raises the problem that emission of light occurs only in part of the light emitting portion formative layer. In the semiconductor light emitting device of the present invention, a superlattice layer is provided between the light emitting portion formative layer and the cathode electrode.