An aperture unit includes a base plate, a cover, a plurality of aperture blades, a drive ring, and protrusions. The aperture blades are disposed between the base plate and the cover, and adjust the amount of light passing through by varying the size of an opening. The drive ring is disposed between the base plate and the cover, and is rotationally driven when the aperture blades are opened and closed. The protrusions are provided to the drive ring and the cover, respectively, and support the aperture blades in the direction of suppressing upward warpage of the aperture blades in a state in which the aperture blades move in the direction of reducing the size of the opening.