A diaphragm device of the present invention includes: a base plate having an aperture portion; a first blade being placed on a plane of the base plate and supported by the base plate to be able to open and close the aperture portion; a second blade being placed on the same plane of the base plate as the first blade, and supported by the base plate to be able to open and close the aperture portion; and a drive ring being formed so as to surround the perimeter of the aperture portion, the driving ring being configured to drive the first blade and the second blade to open and close, wherein the first blade and the second blade perform mutually different actions based on an operation of the drive ring.