An optical element includes a conductive fixed reflection film, a movable reflection film that faces the fixed reflection film, a transmissive second insulating film which is provided on a side of the fixed reflection film opposite to the movable reflection film, and a light receiving unit which is provided on a side of the second insulating film opposite to the fixed reflection film and within a light receiving region where the fixed reflection film, the movable reflection film, and the second insulating film overlap each other in an element plan view when seen from film thickness directions of the fixed reflection film and the movable reflection film, and which receives light emitted from the fixed reflection film.