A projector has a case, a zoom lens, a zoom ring, a control plate, a lodging element, a control rod, and a handle. The case has an opening, and the zoom ring is disposed within the case and nearby the opening, the zoom ring is moved back and forth to drive the zoom rod. The control plate is mounted on the case and laid over the opening movably, the lodging element is movably contacted with the control rod, wherein the handle accepts the force along the extending direction of the rectangular opening so as to let the control plate move the lodging element along the extending direction of the rectangular opening and further to move the control rod for continuously regulating the focal length of the zoom lens.