A variable-magnification optical-system substantially consists of a first-lens-group having positive-refractive-power, a second-lens-group having negative-refractive-power, a third-lens-group having negative-refractive-power, a fourth-lens-group having negative-refractive-power, an aperture-stop, and a fifth-lens-group having positive-refractive-power in this order from an object-side along an optical-axis. The second-lens-group, third-lens-group and fourth-lens-group move when magnification is changed from a wide-angle-end to a telephoto-end. The first-lens-group substantially consists of a 1f-th lens-group having negative-refractive-power, a 1m-th lens-group having positive-refractive-power and a 1r-th lens-group substantially consisting of a 1r1-th lens having positive-refractive-power with its strong convex-surface facing the object-side, a biconvex 1r2-th lens and a convex meniscus 1r3-th lens with its convex-surface facing the object-side, and the 1r-th lens-group having positive-refractive-power as a whole in this order from the object-side. The 1f-th lens-group substantially consists of a concave meniscus-lens with its convex-surface facing the object-side and a negative-lens in this order from the object-side.