A zoom lens system according to the present disclosure includes, in order from an object side to an image plane side, a first lens group having positive optical power; a second lens group having negative optical power; a third lens group having positive optical power; and a subsequent lens group including a fourth lens group, a fifth lens group, and a sixth lens group. The first lens group comprises, in order from the object side, a first lens element having negative optical power; a second lens element having positive optical power; a third lens element having positive optical power; and a fourth lens element having positive optical power. The fifth lens group in the subsequent lens group has negative optical power. The first lens group is fixed with respect to the image plane in zooming from a wide-end to a tele-end upon image shooting.