Zoom optical system, optical device and method for manufacturing the zoom optical system

A method for manufacturing a zoom optical system, comprising:

• arranging, in order from an object side, a first lens group having positive refractive power, a front-side lens group, an intermediate lens group having positive refractive power, and a rear-side lens group,
• wherein the front-side lens group is composed of one or more lens groups and has a negative lens group, at least part of the intermediate lens group is a focusing lens group,
• the rear-side lens group is composed of one or more lens groups,
• the lens groups are arranged in a lens barrel in such a manner that, upon zooming, the first lens group is moved with respect to an image surface, a distance between the first lens group and the front-side lens group is changed, a distance between the front-side lens group and the intermediate lens group is changed and a distance between the intermediate lens group and the rear-side lens group is changed, and
• the following conditional expression is satisfied:
• 0.000<βFw<0.800
• where βFw denotes a lateral magnification of the focusing lens group in the wide-angle end state.