Provided is an optical element wherein optical alignment can be easily performed. This optical element (100) is interposed between an optical transmission line and a light-emitting element or a light-receiving element so that light is transmitted from one side to the other through the optical element. At least one surface of the optical element is provided with a first light collection region anda second light collection region. With an optical path for a light beam passing through the center of the light-emitting element or the light-receiving element, the center of the optical element, andthe center of the end surface of the optical transmission line serving as the optical axis, the surface (105) of the first light collection region is formed so that the light from the one side can bereceived by the other side, and the surface (107) of the second light collection region is formed so that the light from the one side is focused at a prescribed position between the optical element and the other side. The surface of the second light collection region is configured so that the light passing through the second light collection region forms an image of a ring or a part thereof at theprescribed position.