A lens barrel capable of accurately detecting a position of a retractable lens retaining frame. A frame female member for rotating a frame around a lead screw and driving the frame in forward and backward directions along the lead screw is formed with a T-shared protruded member as a detected portion located at a position opposite a rotation-preventing projection. The T-shared member structures a position of the frame together with a transmissive photo-interrupter, to decide a reference position in a retracted state of the frame and for an optical axis entrance completed position of the frame at a time when a transition has changed from a retracted state to a photographable state, and detects a distance from the reference position of the frame or a position of the frame in the photographable state in which a focal distance during wide-angle photographing and telephoto photographing is changed.