Provided is a compact optical element that secures an optical path length and improves manufacturing precision economically. The optical element includes a transparent member having a first and second refracting surface, and reflecting surfaces. Light entering the transparent member from the first refracting surface is reflected by the reflecting surfaces to the second refracting surface. An optical path from the first to second refracting surface crosses itself inside the transparent member seen from a direction perpendicular to light entering the first refracting surface and exiting the second refracting surface. The transparent member guides the incident light from the first to the second refracting surface while reflecting the light alternately by at least one first and one second reflecting surface is in a first and second region respectively. The first and second regions and, respectively, are on opposite sides of a plane passing through the transparent member taken as a boundary.