The invention discloses a flattening device which comprises multiple connecting rods, multiple transverse rods, a spring, a wire pressing column, a supporting frame, a reeling column, a supporting column and a fixing rod, wherein the reeling column, the supporting column and the fixing rod are installed on the supporting frame and arranged in the vertical direction from bottom to top. The two surfaces of a metal band make tight contact with the side face of the wire pressing column and at least part of the side face of the supporting column respectively so that the metal band can be flattened. The connecting rods are arranged in parallel and at least part of each transverse rod penetrates the corresponding connecting rods, so that the connecting rods are connected. The transverse rods at least comprise the first transverse rod and the second transverse rod. One end of the spring is fixedly connected to the second transverse rod and the other end of the spring is fixedly connected to the fixing rod. The rotating direction of the reeling column is opposite to that of the supporting column. By the adoption of the flattening device, the metal band can be flattened before being collected, so that the purposes that reeling efficiency is high and resources are saved are achieved.