A blade open-close device mountable on a module board including a lens unit includes a base including peripheral walls adjacent to the lens unit, a cover plate covering at least part of the base, and a blade movable in a blade chamber between the cover plate and a surface of the peripheral walls. A partition and the cover plate each have an opening aligned with an optical axis of the lens unit. The blade open-close device includes an actuator that moves the blade between a closing position to cover the openings and an opening position to uncover the openings. A distance from the surface of the peripheral walls to a surface of the cover plate opposite to the base along the optical axis is one fifth or less of a total of a thickness of the module board and a height of the lens unit measured along the optical axis.