A zoom lens suitable for imaging an object on a photosensitive element is provided. The zoom lens includes a first lens group, a second lens group disposed between the first lens group and the photosensitive element, a third lens group disposed between the second lens group and the photosensitive element, and a fourth lens group. The second lens group is suitable for moving between the first lens group and the third lens group. The third lens group includes two lenses having positive refractive power. The fourth lens group is disposed and suitable for moving between the third lens group and the photosensitive element. The refractive powers of the first lens group, the second lens group, the third lens group, and the fourth lens group are a positive value, a negative value, a positive value, and a positive value respectively.