A semiconductor light emitting device is disclosed. An emitting layer forming portion for forming an emitting layer made of a compound semiconductor of AlGaInP group or AlGaAs group including a n-type layer, an active layer and a p-type layer laid one on another is formed on a GaAs substrate. Further, a current diffusion layer of GaP is formed on the front surface of the emitting layer forming portion. The p-type layer between the active layer and the current diffusion layer is formed to the thickness of not less than about 2 &mgr;m, or the current diffusion layer is formed to the thickness of about 3 to 7 &mgr;m. As a result, the semiconductor light emitting device of a high luminance is thus realized, in which the distortion due to the lattice mismatch has no effect on the emitting layer.