To obtain the automatic change of the reel in an unwinder, in particular for reels of paper and other materials in web form, operation in which a reel (2) that is nearly empty is replaced with a new reel (2′), wherein provision is made to connect a tail portion (LC) of the web of the nearly empty reel (2) to the head portion (LT) of the web of the new reel (2′) after overlapping of said ends (LC) and (LT), said overlap step begins along the surface of the new reel 2′, right next to the latter.