A zoom lens device has a first lens holding barrel, a second lens holding barrel, the first lens holding frame and the second lens holding frame, all of which is assembled in a fixed barrel. The second lens holding frame holds a fourth lens group. The second lens holding frame is provided with a hole and a long hole, which fit to a first guide shaft and a second guide shaft respectively. The first and second guide shafts are disposed inside the fixed barrel. A first end of the first guide shaft slidably fits on the second lens holding barrel, while a second end is temporarily fixed to the fixed barrel so as not to move in a direction of an optical axis but to move in a direction substantially perpendicular to the optical axis L. By moving the temporarily fixed second end in the direction substantially perpendicular to the optical axis L, the second lens holding frame can move and a decentering adjustment of the fourth lens group will be made. After the decentering adjustment, the second end is ligidly fixed to the fixed barrel with an adhessive agent.