A nipper formed of a pair of nip blocks in an open state suction-holds on nip surfaces thereof a front end of the adhesive tape that is folded back with an edge member and separated from a separator. Then, the nip block on a front end side pivots to unite the nip surfaces of the nip blocks to each other. As a result, the adhesive tape is bent inwardly and adhesive layers thereof are adhered to each other to form a tab. The nip block on a rear end side suction-holds a rear end of the cut adhesive tape. Then, the nip block on the rear end side pivots to bend the adhesive tape inwardly for forming a tab.