Abstract: A mechanism of a band attaching device of a case sealing machine for preventing the band from falling down. A fourth band guiding wheel is disposed under the band stopper boards and movable on the front band pressing wheel support. When the fourth band guiding wheel is positioned at a lowest position, the front edge of the outer surface of the fourth band guiding wheel intersects the band stopper boards and the band is forced to move downward and linearly contact with the band stopper boards on the adhesive face. At this time, the band is urged to forward project into an arch state so as to enhance the upright standing ability of the band without falling down.