A zoom lens, comprising: a first lens group (I) having positive refractive power, a second lens group (II) having negative refractive power, an aperture stop (S), a third lens group (III) having positive refractive power and a fourth lens group (IV) having positive refractive power, wherein the first and third lens groups (I, III) move toward the object side according to a change in magnification power as the zoom lens shifts from a wide-angle position to a telephoto position, the aperture stop (S) moves independently from the lens groups (I, III), and a following formula is satisfied: 0.30