The device for the structural closure and fastening of folders consists of a reciprocal set of coupling means (2a,2b), which, provided with insert fasteners (6,13) and fixation means (9,9a,9b) that are mounted on the edges (23a) of the covers (23), allow the closure of a filing folder (20) which allows to close the filing folders adequately, while keeping their structural integrity and preventing deformations and breaks. It also allows the correction of the deformations in case they occurred.