The two-dimensional photonic crystal surface emitting laser according to the present invention includes a number of main modified refractive index areas periodically provided in a two-dimensional photonic crystal and secondary structures each relatively located in a similar manner to each of the main modified refractive index areas. The location of the secondary structure is determined so that a main reflected light which is reflected by a main modified refractive index area and a secondary reflected light which is reflected by a secondary structure are weakened or intensified by interference.