A negative first group optical system, a positive second group optical system,
and a positive third group optical system are sequentially arranged from the object
side. A stop moving integrally with the second group optical system is provided
on the object side of the second group optical system. The focal length is changed
by changing distances between the group optical systems, and the third group optical
system is moved on an optical axis. The first group optical system includes a negative
meniscus lens, a negative meniscus lens, and a positive lens. The second group
optical system includes a cemented lens of a positive lens and a negative lens,
a positive lens, and a positive lens. The third group optical system includes one
positive lens not including an aspherical surface.