A lens barrel includes an image-capturing optical system having a movable lens and a drive mechanism with a screw member extending along the optical axis direction and being rotated by a motor, a female threaded member moving along the screw member as it revolves. The screw member includes a male screw, and a shaft having an outside diameter equal or less than an inside diameter of a female threaded member, the shaft extending from an end of the male screw, the end being at an opposite direction to a direction in which the engagement section is in abutment with the end of the female threaded member. The female threaded member is disposed such that the female threaded member can move along the male screw and can move from the male screw to a spot on the shaft in abutment with the male screw.