Abstract: An apparatus (1) for deforming a metal bar (2) having a rectangular section up to obtaining a metal bar (2) having a trapezoidal section or a hexagonal section, the metal bar (2) having a rectangular section comprising a first lateral wall (3) and a second lateral wall (4) which are opposite one another, and a third lateral wall (5), the apparatus comprising: a first rotatable roller (11) which has a first conical wall (12); a second rotatable roller (13) which has a second conical wall (14); the first roller (11) and the second roller (13) being arranged with respect to one another such that: the first conical wall (12) and the second conical wall (14) are facing one another; and when the metal bar (2) having a rectangular section crosses a spatial region comprised between the first conical wall (12) and the second conical wall (14) with the relative third lateral wall (5) facing externally, they can press respectively against the first lateral wall (3) and the second lateral wall (4), deforming the metal ba