A semiconductor laser diode having a graded interlayer is provided. The semiconductor laser diode has the graded interlayer between an active layer composed of InGaN and an electron blocking layer (EBL) composed of AlGaN. The graded interlayer is composed of In.sub.xAl.sub.yGa.sub.1-x-yN(0.ltoreq.x.ltoreq.0.2, 0.ltoreq.y.ltoreq.0.5) and is formed by grading a composition of group III materials. Accordingly, the active layer and the p-EBL have a reduced difference in rigidities and lattice parameters, and an abrupt gradient of an energy band and generation of a strain can be avoided in an interface between the active layer and the p-EBL. Since a crack can be prevented from being generated along the interface between the active layer and the p-EBL when a cleavage facet is formed, characteristics of the semiconductor laser diode can be improved.