An imaging optical apparatus with a thin blade containing member for containing a blade member for limiting an opening, having an insertion portion that has an opening; an actuator for causing a blade member to slide; a containing frame for containing the actuator and the blade containing member, except for the insertion portion, having, on an outer edge, a recessed lens frame retaining portion into which the insertion portion; a lens frame, held in the lens frame retaining portion, having an insertion hole, for insertion of the insertion portion so that the center of the opening will be coaxial with the optical axis; and a clip for holding, in cooperation with the containing frame, a lens frame that is held in the lens frame retaining portion, through joining with the containing frame.