To prevent cracking of a cover film more surely, suppress increase of cost, and improve productivity. A seal device comprises: a film reception roll (20) having plural recess parts on an outer periphery; and a heating roll (25) to be pressed against the film reception roll (20). Both films (3, 4) are fed to a space between both rolls (20, 25), therefore a cover film (4) is attached to a container film (3). Plural salient strip parts (61) projecting in a horn-shape, toward the outer periphery direction and disposed so as to form a mesh-state of parallelogram, are disposed on an outer periphery of the heating roll (25). On each area of parallelogram surrounded by the salient strip parts (61) on the outer periphery of the heating roll (25), a stopper part (62) which becomes dent relative to a top part of each salient strip part (61), is provided. When the cover film (4) is attached to the container film (3), the cover film (4) can contact with the stopper part (62).