An object of the present invention is to provide a compact size variable
power optical system capable of producing a high quality image. The
variable power optical system comprises a plurality of lens groups for
forming an optical image on an image surface of an image pickup device.
Among the plurality of lens groups, the first lens group, which is
disposed in the most subject side has a negative refraction power,
includes at least a lens having a negative refraction power and a
reflective optical element for bending the optical axis. When varying the
variable power, the axial distance between the first lens group and the
image surface varies. When Nd denotes the refraction power of the lens
having negative refraction power at d-line, the refraction power
satisfies the conditional formula Nd>1.81.