A method for fabricating a semiconductor light emitting device, the method comprising the steps of: repeatedly forming, on a first nitride based Group III-V compound semiconductor layer, stripe-shaped masking films in a predetermined cycle in a width-wise direction thereof, each masking film comprising first width sections having a predetermined width and second width sections which are adjacent to both ends of each first width section and have a greater width than the predetermined width; selectively growing a second nitride based Group III-V compound semiconductor layer from exposed parts of a surface of the first nitride based Group III-V compound semiconductor so as to cover the masking films and the exposed parts, each of the exposed parts being located between the masking films; and layering a semiconductor laser structure on the second nitride based Group III-V compound semiconductor layer, the semiconductor laser structure including an active layer which substantially extends in a length-wise direction of the masking films and level difference portions which extend in the width-wise direction by a structure in which a portion located above the second width sections is lower than a portion located above the first width sections.