A zoom lens comprising: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; and a fifth lens group having a positive refractive power, wherein the first through fifth lens groups are arranged sequentially from an object side to an image side of the zoom lens, wherein the first lens group comprises a doublet lens and a lens having a positive refractive power, wherein the second lens group comprises a first sub-lens group having a negative refractive power and a second sub-lens group having a negative refractive power that is arranged to perform a focusing function; wherein each of the lens groups is arranged to move when the zoom lens is zoomed.