A zoom lens which is arranged to zoom from a wide-angle mode through an intermediate mode to a telephoto mode, the zoom lens consisting of: 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 lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group 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 (G2-1) having a negative refractive power and a second sub-lens group (G2-2) having a negative refractive power, the second sub-lens group being arranged to perform a focusing function, wherein each of the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group is arranged to move when the zoom lens is zoomed, wherein the second sub-lens group (G2-2) of the second lens group comprises only one lens, characterized in that the zoom lens satisfies the following conditions: 0.4 < BF W / FL W < 1.1, and 0.9 < FL _ RG W / BF W < 1.35, where FL W denotes a total focal length of the zoom lens when the zoom lens is in a wide-angle mode, BF W denotes a back focal length of the zoom lens when the zoom lens is in the wide-angle mode, and FL_RG W denotes a combined focal length of the third lens group, the fourth lens group, and the fifth lens group when the zoom lens is in the wide-angle mode, and in that the fifth lens group comprises a first lens, a second lens, a third lens, an fourth lens, and a fifth lens, the first, second and fifth lenses being positive and the third and fourth lenses being negative, and wherein the first lens, the second lens, the third lens, the fourth lens and the fifth lens are arranged sequentially from an object side to an image side of the fifth lens group. 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 lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group 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 (G2-1) having a negative refractive power and a second sub-lens group (G2-2) having a negative refractive power, the second sub-lens group being arranged to perform a focusing function, wherein each of the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group is arranged to move when the zoom lens is zoomed, wherein the second sub-lens group (G2-2) of the second lens group comprises only one lens, characterized in that the zoom lens satisfies the following conditions: 0.4 < BF W / FL W < 1.1, and 0.9 < FL _ RG W / BF W < 1.35, where FL W denotes a total focal length of the zoom lens when the zoom lens is in a wide-angle mode, BF W denotes a back focal length of the zoom lens when the zoom lens is in the wide-angle mode, and FL_RG W denotes a combined focal length of the third lens group, the fourth lens group, and the fifth lens group when the zoom lens is in the wide-angle mode, and in that the fifth lens group comprises a first lens, a second lens, a third lens, an fourth lens, and a fifth lens, the first, second and fifth lenses being positive and the third and fourth lenses being negative, and wherein the first lens, the second lens, the third lens, the fourth lens and the fifth lens are arranged sequentially from an object side to an image side of the fifth lens group.