A zoom lens, comprising, in order from an object side: a first lens unit having positive refractive power which does not move for varying magnification; a magnification-varying lens unit (U2, U3 or U2, U3, U4) including at least a variator lens unit having negative refractive power and a compensator lens unit which move for varying magnification; an aperture stop; and an imaging lens unit (U4 or U5) having positive refractive power which does not move for varying magnification, wherein: the first lens unit includes, in order from the object side, a first sub-lens unit having positive refractive power, a second sub-lens unit having negative refractive power, and a third sub-lens unit (U 13) having positive refractive power; and the third sub-lens unit includes a movable sub-third sub-lens unit (U13f) having positive refractive power; characterized in that the second sub-lens unit and the sub-third sub-lens unit (U13f) constituting a floating focus system as lens units thereof are respectively driven to the object side so as to perform focus adjustment to an object at a short distance; and the following expressions are satisfied: − 2.5 < f 12 / f 13 f < − 0.4; and 0.05 < δ × 13 f / δ × 12 < 5.0, where f12 represents a focal length of the second sub-lens unit, f13f represents a focal length of the sub-third sub-lens unit, δx12 represents a drive amount of the second sub-lens unit in focus adjustment from infinity to close range, and δx13f represents a drive amount of the sub-third sub-lens unit in focus adjustment from infinity to close range. a first lens unit having positive refractive power which does not move for varying magnification; a magnification-varying lens unit (U2, U3 or U2, U3, U4) including at least a variator lens unit having negative refractive power and a compensator lens unit which move for varying magnification; an aperture stop; and an imaging lens unit (U4 or U5) having positive refractive power which does not move for varying magnification, wherein: the first lens unit includes, in order from the object side, a first sub-lens unit having positive refractive power, a second sub-lens unit having negative refractive power, and a third sub-lens unit (U 13) having positive refractive power; and the third sub-lens unit includes a movable sub-third sub-lens unit (U13f) having positive refractive power; characterized in that the second sub-lens unit and the sub-third sub-lens unit (U13f) constituting a floating focus system as lens units thereof are respectively driven to the object side so as to perform focus adjustment to an object at a short distance; and the following expressions are satisfied: − 2.5 < f 12 / f 13 f < − 0.4; and 0.05 < δ × 13 f / δ × 12 < 5.0, where f12 represents a focal length of the second sub-lens unit, f13f represents a focal length of the sub-third sub-lens unit, δx12 represents a drive amount of the second sub-lens unit in focus adjustment from infinity to close range, and δx13f represents a drive amount of the sub-third sub-lens unit in focus adjustment from infinity to close range. the first lens unit includes, in order from the object side, a first sub-lens unit having positive refractive power, a second sub-lens unit having negative refractive power, and a third sub-lens unit (U 13) having positive refractive power; and the third sub-lens unit includes a movable sub-third sub-lens unit (U13f) having positive refractive power; characterized in that the second sub-lens unit and the sub-third sub-lens unit (U13f) constituting a floating focus system as lens units thereof are respectively driven to the object side so as to perform focus adjustment to an object at a short distance; and the following expressions are satisfied: − 2.5 < f 12 / f 13 f < − 0.4; and 0.05 < δ × 13 f / δ × 12 < 5.0, where f12 represents a focal length of the second sub-lens unit, f13f represents a focal length of the sub-third sub-lens unit, δx12 represents a drive amount of the second sub-lens unit in focus adjustment from infinity to close range, and δx13f represents a drive amount of the sub-third sub-lens unit in focus adjustment from infinity to close range.