A lens barrel includes a holder holding an image pick-up device; a stationary barrel having a female helicoid; a gear/helicoid ring including an annular rib, a male helicoid formed on the annular rib and engaged with the female helicoid, and a spur gear formed on the male helicoid; a pinion engaged with the spur gear; a linear guide ring provided around the gear/helicoid ring; a outer circumferential groove formed on the gear/helicoid ring; and bayonet lugs projecting rearwards from the linear guide ring and engaging in the circumferential groove. Rotation of the gear/helicoid ring causes a lens group to move along the optical axis. At least a portion of a rear end of the male helicoid extends rearwards. At least a portion of the rear extension portion overlaps the holder in the optical axis direction when the gear/helicoid ring stops retracting at a predetermined position.