To provide a sealing device that prevents unsatisfactory bundling such as sealing failure or band displacement caused by a distorted curve by further providing an auxiliary mechanism that aids in pressing a bundle of sheets of paper when a distorted curve is formed in the bundle.

A bundle 8 of sheets of paper is stacked on cover device 1 and 1, and is pressed by a sweeper 2 from above, and curves. A drive motor 3 is driven and a link mechanism 4 is rotated counterclockwise. At this time, a clamper 5 approaches the direction of the bundle 8 of sheets of paper. In addition, since rotors 62 and 62 hold the rail 52 of the clamper 5 therebetween, an arm 6 starts to rotate counterclockwise around a support 61, and a pusher 7 approaches the bundle 8 of sheets of paper. Further, the link mechanism 4 rotates, and an arm projection 63 runs onto a rotor 43. As a result, a rotating motion is applied to the clamper 5 in addition to a linear motion, and the projection of the pusher 7 runs onto the rotor 62 of the arm 6. Consequently, in the pusher 7, an auxiliary projection 71 for pressing the bundle of sheets of paper appears from a pressing face 51a.