A zoom lens includes a first lens band having a positive focal length, a second
lens band having a negative focal length, and at least third to fifth lens bands
having positive focal lengths. An aperture diaphragm is located in the vicinity
of the third lens band. When magnification i.e., zooming is performed from short
to long focal point ends, the second lens band smoothly moves toward the third
lens band and the fourth lens band simultaneously moves from the fifth lens band
side toward a long focal point end so as to share a magnification function together
with the second lens band.