A light sensor for detecting brightness of an outside of a vehicle includes: a light shielding element on a windshield; a light guiding element in a through hole of the light shielding element; and a light receiving element that receives light from the outside of the vehicle via the light guiding element and the windshield. The light guiding element includes an entrance surface facing the windshield and an output surface facing the light receiving element. The entrance surface receives the light from the outside. The light guiding element transmits and outputs the light from the output surface toward the light receiving element. The entrance surface has a top disposed inside of the through hole.