Three or more lens groups including a negative first lens group and a positive second lens group in this order from an object side are provided. The first lens group is composed of two or more lenses. At least three lens groups are composed of single lens elements, namely, only a single lens, a cemented lens, or a lens in which adjacent lenses are integrated with each other in a fixed manner. This variable power optical system has a power ratio of about two to three, and is compact and high-definition.