A zoom lens includes a movable barrel mounting a lens holder barrel having a focusing lens element for rotational and axial movement therein and a cam barrel mounting the movable barrel for rectilinear axial movement therein. The movable barrel is axially moved for zooming through slide engagement between zooming cam slots of the cam barrel and rectilinear axial guide slots of a stationary barrel when the cam barrel rotates and allows the lens holder barrel to axially moves through helicoids coupling. The movable barrel is provided with a moving range restrictive structure having a plurality of screw holes and a single screw pin selectively screwed in one of the screw holes for focus adjustment. The screw pin is exposed to the outside of the zoom lens all at once when the cam barrel is in a telephoto or wide-angle position or one by one during rotation of the can barrel.