A variable magnification optical system substantially consists of a first lens-group having positive refractive-power, and which is fixed during magnification change, 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, which is fixed during magnification change, and a fifth lens-group having positive refractive-power, and which is fixed during magnification change, in this order from an object-side along an optical-axis. The second, third and fourth lens-groups move in such a manner that a distance between the first lens-group and the second lens-group constantly becomes longer and a distance between the second lens-group and the third lens-group constantly becomes longer, compared with a wide-angle end, and a distance between the third lens-group and the fourth lens-group and a distance between the fourth lens-group and the fifth lens-group change when magnification is changed from the wide-angle end to a telephoto end.