An aperture device for use in an optical apparatus has a plurality of aperture blades which cooperate in collectively defining an aperture of a desired size. The inner edge of at least one of such blades defining one side of the aperture is uneven over at least part of the length of the inner edge. The spacing between adjacent relatively high portions and relatively low portions, as well as the depth, is smaller than the exposed length of the inner edge of each aperture blade when the aperture device has been operated to the minimum aperture size. Preferably, the spacing between adjacent crests or between adjacent high portions and low portions of the unevenness varies in a non-periodic manner.