lens convex on its object side an aperture stop s a second lens group g 2 having positive refracting power and composed of a double convex positive lens and a doublet consisting of a positive meniscus lens convex on its object side and a negative meniscus lens convex on its object side and a third lens group g 3 composed of one double convex positive lens upon zooming from the wide angle end to the telephoto end of the zoom lens the first lens group g 1 moves in a convex locus toward the image plane side of the zoom lens and is positioned slightly nearer to the image plane side at the telephoto end than at the wide angle end the second lens group g 2 moves together with the aperture stop s toward the object side of the zoom lens and the third lens group g 3 remains fixed three aspheric surfaces are used one at the image plane side surface of the negative meniscus lens in the first lens group g 1 one at the object side surface of the double convex positive lens in the second lens group g 2 and one at the image plane side surface of the double convex positive lens in.