A distributed feedback semiconductor laser which has periodic corrugations formed in a light emitting layer or an adjoining layer to extend in the direction of travel of light. A window region formed by a semiconductor layer larger in energy gap than the light emitting layer is provided on the extension line of one end of a laser region formed in the light emitting layer. The length of the window region is so limited as to prevent substantial reflection of laser output light in the window region. The end face of the laser on the opposite side from the window region is coated with a film for increasing reflectivity.