A zoom lens includes, in order from its object side, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, a third lens unit having a negative refracting power, and a fourth lens unit having a positive refracting power. The zoom lens further includes an aperture stop disposed between the first lens unit and the third lens unit. During zooming from the wide angle end to the telephoto end, distances between the lens units change, the first lens unit moves first toward the image side and thereafter toward the object side, the second lens unit moves in such a way as to be located closer to the object side at the telephoto end than at the wide angle end, the distance between the second lens unit and the third lens unit is larger at the telephoto end than at the wide angle end, and the aperture stop moves in such a way as to be located closer to the object side at the telephoto end than at the wide angle end. The second lens unit and the third lens unit satisfy certain conditions.