A zoom lens barrel is a lens barrel having a plurality of lens groups that change intervals in the direction of an optical axis at the time of a zooming operation and move in one-piece toward the optical axis at the time of a focusing operation thereby fixing the mutual intervals in the direction of the optical axis. Furthermore, the zoom lens barrel drives a second group lens frame toward the optical axis via a cam follower by a three-dimensional cam that rotates around the optical axis at the time of the zooming operation and moves toward the optical axis at the time of the focusing operation to perform zooming or focusing. According to this zoom lens barrel, it becomes possible to make the radial size small and further to easily maintain good optical performance.