A semiconductor light emitting device has in sequence on a semiconductor substrate, a multilayer reflection film, a semiconductor layer, and a quantum well active layer. A distance between an upper surface of the multilayer reflection film and a lower surface of the quantum well active layer is 2.lambda./n or less, where .lambda. is a light emission wavelength and n is an average refractive index of the semiconductor layer disposed in between the multilayer reflection film and the quantum well active layer. A phase difference between a reflected ray of light reflected by the multilayer reflection film and an emitted ray of light from the quantum well active layer is a multiple of 2.pi.. In an emission spectrum of the semiconductor light emitting device, two troughs caused by interference between the emitted ray of light and the reflected ray of light appear in the both sides of a main peak. Therefore, the troughs are unlikely to match the main peak, and the peak wavelength of the semiconductor light emitting device can be sustained. Thus, the semiconductor light emitting device stably obtains a specified peak wavelength even when there is slight variance in the distance between the upper surface of the multilayer reflection film and the lower surface of the quantum well active layer.