A bending device for simultaneously forming at least two parallel corrugations in a metal sheet, the bending device comprising: - a lower frame; - an upper frame mounted with the ability to move vertically with respect to the lower frame between a rest position and a bending position; - at least a first and a second dies (15, 16, 17) borne by the lower frame and each comprising a cavity parallel to the cavity of the other die and corresponding to the shape of one of the corrugations that is to be formed; the first die being fixed with respect to the lower frame and the second die (15, 17) being mounted with the ability to slide on the lower frame in a direction transverse to the direction of the corrugations that are to be formed, between a spaced-apart position and a close-together position with respect to the first die; said second die (15, 17) being returned towards its spaced-apart position by a return member; - at least a first and a second punches (12, 13, 14) which are parallel and carried by the upper frame respectively above the first and above the second dies (15, 16, 17), the first punch being fixed with respect to the upper frame and intended to engage inside the cavity of the first die when the upper frame moves from its rest position towards its bending position so as to press the metal sheet, and the second punch (12, 14) being mounted with the ability to slide on the upper frame in a direction transverse to the direction of the corrugations that are to be formed, between a spaced-apart position and a close-together position with respect to the first punch and being intended to engage inside the cavity of the second die (15, 17) when the upper frame moves towards its bending position so as to press the metal sheet, said second punch (12, 14) being returned towards its spaced-apart position by a return member; - the bending device being designed in such a way that, in operation, the movement of the upper frame towards its bending position is able to cause the metal sheet to be bent between the first punch and the first die, on the one hand, and between the second punch (12, 14) and the second die (15, 17) on the other hand, so that said metal sheet transmits a pulling force to the second punch (12, 14) and to the second die (15, 17) which moves them from their spaced-apart position toward their close-together position. - a lower frame; - an upper frame mounted with the ability to move vertically with respect to the lower frame between a rest position and a bending position; - at least a first and a second dies (15, 16, 17) borne by the lower frame and each comprising a cavity parallel to the cavity of the other die and corresponding to the shape of one of the corrugations that is to be formed; the first die being fixed with respect to the lower frame and the second die (15, 17) being mounted with the ability to slide on the lower frame in a direction transverse to the direction of the corrugations that are to be formed, between a spaced-apart position and a close-together position with respect to the first die; said second die (15, 17) being returned towards its spaced-apart position by a return member; - at least a first and a second punches (12, 13, 14) which are parallel and carried by the upper frame respectively above the first and above the second dies (15, 16, 17), the first punch being fixed with respect to the upper frame and intended to engage inside the cavity of the first die when the upper frame moves from its rest position towards its bending position so as to press the metal sheet, and the second punch (12, 14) being mounted with the ability to slide on the upper frame in a direction transverse to the direction of the corrugations that are to be formed, between a spaced-apart position and a close-together position with respect to the first punch and being intended to engage inside the cavity of the second die (15, 17) when the upper frame moves towards its bending position so as to press the metal sheet, said second punch (12, 14) being returned towards its spaced-apart position by a return member; - the bending device being designed in such a way that, in operation, the movement of the upper frame towards its bending position is able to cause the metal sheet to be bent between the first punch and the first die, on the one hand, and between the second punch (12, 14) and the second die (15, 17) on the other hand, so that said metal sheet transmits a pulling force to the second punch (12, 14) and to the second die (15, 17) which moves them from their spaced-apart position toward their close-together position.