A distributed feedback semiconductor laser which has periodic corrugations formed in a layer adjoining a light emitting layer so as to extend in the direction of travel of light and performs laser oscillation by the injection of current into the light emitting layer, in which a part of at least one metal electrode has a TM mode suppressing region disposed at a position where light is essentially distributed in the thickwise direction of the laser. A window region formed of a semiconductor larger in energy gap than the light emitting layer is disposed at both ends of the laser oscillation region in the direction of travel of light, the length of the window region being limited so that no substantial reflection occurs therein.