A zoom lens system of the present invention has a plurality of lens units each composed of at least one lens element and, in order from the object side to the image side, comprises: a first lens unit having negative optical power and composed of two lens elements; a second lens unit having positive optical power; and a third lens unit having positive optical power, wherein in zooming, at least the first lens unit and the second lens unit move along an optical axis, on the image side relative to the second lens unit, an aperture diaphragm is arranged that moves along the optical axis integrally with the second lens unit during zooming, the second lens unit moves in a direction perpendicular to the optical axis, and the condition is satisfied: 1.00 4.0, ωW>35, m2W, m3W: lateral magnifications of the second and third lens units at a wide-angle limit in an infinity in-focus condition, fT, fW: focal lengths of the entire system at a telephoto limit, a wide-angle limit, ωW: a half value of maximum view angle at a wide-angle limit.