A lens barrel which can increase the relative movement interval of lens units in the direction of an optical axis without increasing the dimension of a translating cylinder, which inhibits the rotation of the lens units, in the direction of the optical axis. The movement of a second lens unit holding second group lenses is switched from linear guide by a first translating guide unit to linear guide by a second translating guide unit when the second lens unit moves in a direction relatively away from a first lens unit holding first group lenses.