A lens barrel includes lens groups, lens retaining frames retaining the lens groups, respectively, between a collapsed state and a photographic state are moved toward an object side, a movable cylinder retaining the plurality of lens retaining frames therewithin, and a driving mechanism to move the lens retaining frames. The driving mechanism includes a main guide shaft parallel to the photographic axis and supports a retractable lens retaining frame retaining a retractable lens group movably along and rotatably about the main guide shaft, a lead screw disposed in parallel with the main guide shaft and to be driven to rotate, a screw member to be screwed on the lead screw by coming into contact with the lead screw in directions perpendicular to the lead screw to be moved along the lead screw by a rotation of the lead screw, and a cam structure connecting the retractable lens retaining frame with the screw member to convert a movement of the screw member along the lead screw into a rotary motion of the retractable lens retaining frame about the main guide shaft and a linear motion of the retractable lens retaining frame along the main guide shaft.