A distributed feedback semiconductor laser which has periodic corrugations in a light emitting layer or an adjoining layer in the direction of travel of light and performs laser oscillation by the injection of carriers into said light emitting layer. In accordance with the present invention, there are provided, in the neighborhood of the center of a laser region, a region for changing the phase of the periodic corrugations by about 180 degrees, and, on the extension of the laser oscillation region at both sides thereof, a window region formed of a semiconductor larger in energy gap but smaller in refractive index than the light emitting layer, the length of the window region being so limited as to prevent substantial reflection of laser output light in the window region.