A semiconductor light emitting device includes: a first cladding layer made of a first conductivity type group III nitride semiconductor; an active layer formed on the first cladding layer; a quantum well electron barrier layer which is formed on the active layer, and includes electron trapping barrier layers made of AlxbGaybIn1-xb-ybN (0≦xb<1, 0<yb≦1, 0≦1-xb-yb<1), and two or more electron trapping well layers made of AlxwGaywIn1-xw-ywN (0≦xw<1, 0<yw≦1, 0≦1-xw-yw<1); and a second cladding layer which is formed on the quantum well electron barrier layer, and is made of a second conductive type group III nitride semiconductor. Each of the electron trapping well layers is formed between the electron trapping barrier layers, and band gap energies of the electron trapping well layers increase with decreasing distance from the active layer.