A zoom lens driving mechanism is disclosed that is adapted to rotate a first driving lens barrel and a second driving lens barrel relative to each other and thereby to move a movable lens barrel back and forth in parallel to an optical axis. More specifically, a linearly movable member that is provided to guide a linear movement of the movable lens barrel relative to the second driving lens barrel, is moved back and forth under a guidance by a leading groove formed in the first driving lens barrel. With such a unique arrangement, no part is required to support the linearly movable member, and therefore, any apprehension about the strength of a part as well as a flare phenomenon can be avoided.