A lens apparatus includes a lens barrel, an image-capturing optical system, and a diaphragm device disposed in an optical path of the image-capturing optical system. The diaphragm device includes a plurality of diaphragm blades and an electroactive polymer actuator configured to move the plurality of diaphragm blades from a diaphragm-open state to a diaphragm-closed state and from a diaphragm-closed state to a diaphragm-open state.