An optical unit includes: a base which includes a main surface; a mirror device which includes a movable mirror portion and is disposed on the base; a frame member that is provided on the main surface so as to surround the mirror device; and a window member that is bonded to the frame member and has a flat plate shape. The frame member includes a first wall portion which is provided on the main surface and includes a first top surface on the side opposite to the main surface, a second wall portion which is provided on the main surface so as to face the first wall portion and includes a second top surface on the side opposite to the main surface.