The invention is concerned with a zoom lens that is well fit for a digital type single-lens reflex camera, has improved optical performance, and is bright all over the zooming zone. The zoom lens comprises a first group G1 of positive power, a second group G2 of negative power and a third group G3 of positive power. Upon zooming, the first group G1 remains fixed, and the second G2 and the third group G3 are movable. The first group G1 comprises a subgroup 1A of negative power and a subgroup 1B of positive power, and the second group G2 comprises a first negative lens, a cemented positive lens, a second negative lens and a third negative lens. The zoom lens satisfies conditions (1) and (2) with respect to the focal length of the subgroup 1A and the focal length of the second group G2.