A lens barrel includes a fixed cylinder fixed to an imaging device body, a lens-holding frame, and a movable cylinder for supporting the lens-holding frame movably in an optical axial direction, in which the movable cylinder is located at a position collapsed relative to the fixed cylinder in a non-imaging mode while the movable cylinder is extended from the collapsed position to a zooming region in an imaging mode, and then the movable cylinder moves in the optical axial direction within the zooming region.