To provide a buffer device and the like which is installed between a writing part for writing an image on a long sheet while conveying the sheet and a post-processing part (a drying part), thereby preventing the uneven transport occurring in the post-processing part from being transmitted to the writing part.SOLUTION: In a buffer device, a buffering tower 30 comprises a storage chamber 31, an edge guide 34, and a back-tension applying part 33. The storage chamber 31 houses a sheet P in a downwardly curved shape. The edge guide 34 performs positioning in the width direction of the sheet by winding the sheet on a roll 334 and guiding the edge of the sheet by a guide plate 332. Further, the back-tension applying part 33 draws the sheet by a fan 331 and sucks it onto the guide plate 332 having a large number of apertures. Accordingly, the back-tension applying part 33 serves as a resistance to conveyance when the sheet is conveyed by a driving roller 44, increases the rigidity of the sheet P wound around the roll 341, and prevents buckling of the sheet caused when the edge of the sheet comes into contact with a guide plate 342.SELECTED DRAWING: Figure 1