A zoom lens system includes plural optical units each of which includes plural optical elements each having a rotationally asymmetrical surface, and changes optical power as the optical elements in each of the plural optical units move in directions different from an optical axis, wherein a principal point position moves in an optical-axis direction without causing the optical element to move in the optical-axis direction, the zoom lens system having such a shape that the principal point position of at least one unit of the plural optical units is located outside the one unit.