A light concentrating optical element includes: a substrate; and a plurality of micro-optical members dispersed inside the substrate. The plurality of micro-optical members each direct light having been transmitted through the substrate and having entered a micro-optical member along an entering direction, so that the light exits the micro-optical member along a matching direction matching the entering direction, and direct light having entered the micro-optical member along an other entering direction, so that the light exits the micro-optical member along an exiting direction, resulting in an advancing direction of light having entered the substrate through a substrate front surface and advancing through the substrate being deflected via the plurality of micro-optical members to extend along the matching direction; and the light having been deflected so as to advance through the substrate along the matching direction is concentrated at an end area of the substrate.