A zoom lens includes a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power. During zooming from a wide-angle end to a telephoto end, each lens unit moves so that a distance between the first lens unit and the second lens unit increases, and a distance between the second lens unit and the third lens unit decreases. Each of the first lens unit, the second lens unit, and the third lens unit consists of a single positive lens and a single negative lens, and the fourth lens unit consists of a single positive lens. Focal lengths of the entire zoom lens at the wide-angle end and the telephoto end and focal lengths of the first lens unit and the second lens unit are appropriately set.