At least one exemplary embodiment is directed to a zoom lens which includes, in order from an object side to an image side, a first lens unit having positive refractive power and is stationary during zooming, a second lens unit configured to move to perform zooming, a third lens unit configured to move to compensate for variation of an image plane caused by zooming, and a fourth lens unit having positive refractive power and is also stationary during zooming. The first lens unit includes, in order from the object side to an image side, a first lens subunit having positive refractive power and is stationary during focusing, a second lens subunit having positive refractive power, and a third lens subunit having negative refractive power and is also stationary during focusing. The second lens subunit moves along an optical axis during focusing.