The reflector is provided with plural reflector units. Each reflector unit is shaped as a prism or a cylinder provided with a retroreflective structure at one end, the retroreflective structure is configured to reflect incident rays from the other end of the prism or the cylinder in a direction of incidence, and in a reference cross section of the reflector unit, the reference cross section containing the central axis of the prism or the cylinder and the reference cross section being determined such that the shape of the retroreflective structure is line-symmetric with respect to the central axis in the reference cross section, the shape of a light receiving surface at the other end is line-symmetric with respect to the central axis and has a portion inclined with respect to a direction perpendicular to the central axis in the reflector unit.