To provide a zoom lens barrel that changes the aperture diameter to a larger or smaller diameter in a zoom photographing area by a variable aperture diaphragm mechanism and causes one of movable lens groups to enter the aperture, with a larger aperture in an accommodated position, the zoom lens barrel being configured so that before a diaphragm opening operation for making a diaphragm aperture larger is completed, the lens group is prevented from entering the aperture and colliding with it.

In the zoom lens barrel, the variable aperture diaphragm mechanism satisfies the following conditions: the aperture diameter is switched between the larger and the smaller ones by the normal and the reverse rotating operations of the opening/closing ring; when an aperture control lens group formed from one of the movable lens groups is moved from a zoom photographing position to the accommodated position, the opening/closing ring is rotated so that the aperture of the variable aperture diaphragm mechanism is changed from the smaller aperture to the larger aperture; in the accommodated position, a part of the aperture control lens group is close to the variable aperture mechanism and enters the large aperture; and a proximity regulating member is provided, the proximity regulating member being configured such that when the aperture control lens group is close to the variable aperture diaphragm mechanism with the opening/closing ring being in the smaller aperture position, the maximum proximity between both sides is regulated.