Provided is a variable magnification optical system comprising, in order from an object side along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4; upon zooming from a wide angle end state to a telephoto end state, a distance between the first lens group G1 and the second lens group G2 being varied, a distance between the second lens group G2 and the third lens group G3 being varied, and a distance between the third lens group and the fourth lens group being varied; the third lens group G3 comprising, in order from the object side along the optical axis, a 3a-th lens group G3a having positive refractive power, an aperture S, and a 3b-th lens group G3b having positive refractive power; a lens group having negative refractive power within the 3b-th lens group G3b being used as a vibration reduction lens group and moved so as to include a component in a direction orthogonal to the optical axis, whereby image plane correction is performed when image blurring occurs; and predetermined conditions being satisfied. Whereby, a small-size and high-performance variable magnification optical system, capable of realizing a small variation in aberration and attaining a sufficient brightness even in the telephoto state, an imaging apparatus, and a method for manufacturing the variable magnification optical system are provided.