A lens apparatus includes an optical system, a lens barrel, and a weight. The optical system includes a movable lens unit. The lens barrel houses the optical system and includes a fixed barrel and a cam barrel. The fixed barrel supports the movable lens unit to be forwardly and backwardly movable along the optical axis of the optical system. The cam barrel is engaged with the movable lens unit, is supported by the fixed barrel to be rotatable around the optical axis, and is configured to forwardly and backwardly move the movable lens unit in accordance with the rotation of the cam barrel. The weight is engaged with the cam barrel and forwardly and backwardly moves along the optical axis in a direction opposite to a moving direction of the movable lens unit in accordance with the rotation of the cam barrel.