An optical unit includes: a cylindrical member whose thickness varies in a circumferential direction a transparent member disposed at one end, in an axial direction, of the cylindrical member and a joining member which joins the transparent member to the cylindrical member and thereby seals the cylindrical member at the one end in the axial direction, and a portion, joining a side surface of the transparent member to an inner circumferential surface of the cylindrical member, of the joining member is thicker at a position where the cylindrical member is thick than at a position where the cylindrical member is thin.
