A lens barrel with a lock arranged to avoid loosening the lock and defocusing the lens barrel when vibrated during focusing and zooming. The lens barrel includes a fixed cylinder, an adjustment ring, lock screws and a lock ring, lock screws and a lock ring. The adjustment ring is slidably attached to the fixed cylinder so as to rectify locations of optical components along the optical axis. The lock screws in screw holes extend at one end of the fixed cylinder in parallel with the optical axis, and each lock screw has a part that serves as a turning force transmitting segment and moves along the optical axis at the end of the fixed cylinder. The lock ring is slidably attached to the end of the fixed cylinder and has an inner surface that is mated with the force transmitting segment to let the lock screws rotate to secure the adjustment ring to the fixed barrel.