A high zoom-ratio zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a positive fifth lens group, and a negative sixth lens group, in this order from an object.Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the positive first lens group and the negative second lens group increases, and a distance between the negative second lens group and the positive third lens group decreases.The high zoom-ratio zoom lens system satisfies the following conditions: 5.0