An embodiment of this invention provides a zoom lens, which primarily includes, in order from an object side to an image-forming side, a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having positive refractive power; a fifth lens group having negative refractive power; and a sixth lens group having positive refractive power; wherein the first lens group comprises a prism, and the second lens group, the fourth lens group, and the fifth lens group are moved toward the third lens group along an optical axial for zooming from a wide-angle end to a telephoto end.