The invention aims to provide a zoom lens which achieves a longer focal length and has a shorter optical overall length at the telephoto end, and to provide an imaging apparatus provided with the zoomlens. To this end, such a zoom lens is formed, which includes, in order from an object side, a positive first lens group G1, a negative second lens group G2, a composite positive lens group which includes, at the most object side, a positive third lens group G3, which is only consisting of one or more lens groups having positive refractive power, and which has positive refractive power as a whole, and a composite negative lens group which includes, at the most object side, a negative A lens group, which additionally includes at least a negative B lens group, and which has negative refractivepower as a whole. In the zoom lens, changing focal length is performed by varying the distances between the lens groups, and a predetermined condition is satisfied.