To provide a light quantity-adjusting device which achieves smooth driving free from collision or connection of light-shielding blades even when the light-shielding blades are driven at high speed without adding a special member, and to provide an imaging apparatus in which the light quantity-adjusting device is mounted.

The light quantity-adjusting device includes: a bottom plate having an opening through which light passes; a plurality of light-shielding blades supported to be freely turned on the bottom plate, and changing area of the opening; and a driving means for driving the light-shielding blades. Each of the light-shielding blades is turned in a direction in which the area of the opening is decreased, while overlapping with the other light-shielding blade, so that its end may cross the other light-shielding blade by the driving means. In the end crossing with the light-shielding blades, at least one of chamfering and R attachment is provided.