The utility model relates to a rolling film material flatness detection device. The device comprises a rack, a reel shaft, and a film material detection unit used for detecting size of an uneven area on the film material. The reel shaft is divided into a first reel shaft and a second reel shaft that are parallel to each other. The top parts of the first and second reel shafts are in the same horizontal surface. The device further comprises a reel support that allows a film reel to be disposed below the horizontal surface in a direction parallel to the first reel shaft. The reel support is disposed at the end, which is provided with the first reel shaft, of the rack. The end, which is provided with the second reel shaft, of the rack is provided with a load unit used for applying a stretching load vertical to the film reel shaft onto the film material winding the second reel shaft. The device easily ensures parallelism between the two reel shafts, prevents multiple reel of the reel shaft in the prior art from influencing the film material, and then prevents the film material from being distorted and deformed. The device is convenient in installation and adjustment.