The present edge-emitting semiconductor layer element includes two-dimensional photonic crystals 4 formed in a semiconductor layer, and when one direction of a contact region of an electrode 8 is provided as a length direction (X-direction) and a direction perpendicular to both of the length direction and a thickness direction of a substrate is provided as a width direction (Y-direction), the two-dimensional photonic crystals 4 are, when viewed from a direction (Z-axis) perpendicular to the substrate, located in a region containing the electrode contact region and wider in the width direction than the contact region, and have a refractive index periodic structure in which the refractive index satisfies a Bragg's diffraction condition while periodically changing at every interval along the one direction (X-axis).