A zoom lens system has a front lens group and a rear lens group along the optical axis and in order from the object side. The rear lens group has a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, and a third lens unit having a positive refracting power. Upon zooming from a wide-angle end state to a telephoto end state, a space between the front lens group and the first lens unit varies, a space between the first lens unit and the second lens unit increases, and a space between the second lens unit and the third lens unit decreases. At least a part of the second lens unit is movable so as to have a component in a direction perpendicular to the optical axis.