A zoom lens includes, a first lens unit (1) having a positive refractive power and is fixed with respect to an image plane; a second lens unit (2) having a negative refractive power and causing a variable power action when moved along an optical axis; an aperture stop (6) fixed with respect to the image plane; a third lens unit (3) having a positive refractive power and fixed with respect to the optical axis direction when zooming and when focusing; a fourth lens unit (4) having a negative refractive power and fixed with respect to the image plane; and a fifth lens unit (5) having a positive refractive power and moveable along the optical axis such that the image plane, which is displaced by a movement of the second lens unit along the optical axis and by a movement of the object, is maintained at a constant position from a reference plane. The entire third lens unit is moveable in a direction perpendicular to the optical axis. A condition, 0.035<|.beta.w.beta.t/Z|<0.075, is satisfied, where .beta.w: magnification ratio of the second lens unit at the wide-angle end; .beta.t: magnification ratio of the second lens unit at the telephoto end; and Z: zoom ratio.