To provide a zoom lens that is inexpensive, compact and light in weight and giving high optical performance, to provide an imaging apparatus provided with the zoom lens, and to provide a method for varying the power of the zoom lens.

The zoom lens comprises a first lens group G1 having negative refractive power; a second lens group G2 having positive refractive power; a third lens group G3 having negative refractive power; and a fourth lens group G4 having positive refractive power, in the order starting from the object side, wherein at varying of the power starting from wide-angle end state to telephoto end state, the distance between the first lens group G1 and the second lens group G2 shrinks, the distance between the second lens group G2 and the third lens group G3 widens and the distance between the third lens group G3 and the fourth lens group G4 expands, the second lens group G2 constitutes two positive lenses or fewer and a single negative lens, the fourth lens group G4 constitutes two positive lenses or fewer and a single negative lens, and the prescribed conditional expressions are satisfied.