A stop apparatus includes blades each having a drive pin, a support member supporting pivot members of the blades, and a cam member having cams engaging with the drive pins. The blades form an aperture. The cam member includes cams of which the largest radial distances from the center of the aperture are different from each other. The blades include first blades and second blades. The radial distance from the center of the drive pins of the first blades and that of the drive pins of the second blades are different from each other in an open aperture state. The pivot members of the first and second blades are disposed at positions at a radial distance from the center shorter than the radial distance from the center of a drive pin having the longest radial distance from the center in the open aperture state among the drive pins.