The invention relates to a buffer device (20) adapted to receive a web (2) from a relative source (4) and arranged upstream, with respect to an advancement direction of said web (2) along a relative feed path (FP), of driving means (7) intermittently actuatable to alternately move, and terminate movement of, the web (2) at an operating station (5) arranged further downstream thereof; the buffer device comprising a first and a second group (21a, 21b) of guide rollers (22a, 22b) having different diameters, wherein each roller (22a) belonging to the first group (21a) is paired with a corresponding roller (22b) in the second group (21b) to form a couple of same-diameter rollers; the buffer device (20) comprising means (24) for kinematically coupling the first and second groups (21a, 21b) to one another, so that they are movable in opposite directions relative to one another and symmetrically relative to a central portion (23) of the buffer device (20); and by comprising actuating means (26) for energising the kinematic coupling means (24) to selectively vary the mutual distance of the first and second groups (21a, 21b).