A folding apparatus of a continuous web advancing in a plant for the production of absorbent hygiene articles and intended to be folded into a "V" or "U" shape in a first and in a second longitudinal portion (101, 102) according to a longitudinal folding line parallel to a feeding line of the continuous web, said folding apparatus comprising a folding section comprising a contact unit for the continuous web extending along the feeding line of the continuous web and defining the folding line; a first guide and a second guide which are positioned on opposite sides of the contact unit and respectively having a first sliding surface for the continuous web and a second sliding surface for the continuous web, wherein the first sliding surface of the first guide and the second sliding surface of the second guide extend along said feeding line, they each have a respective infeed section (51, 61), where the web is not folded, and a respective outfeed section (52, 62), positioned downstream of the respective infeed section (51, 61) according to a web feeding direction, where the continuous web is folded in two and has the first portion and the second portion set at an angle to each other, the infeed sections (51, 61) of the first and the second sliding surfaces being substantially coplanar the outfeed section of the first sliding surface and the outfeed section of the second sliding surface being transversal, preferably orthogonal, to the respective infeed sections (51, 61) and at least partly converging in the feeding direction of the continuous web, characterised in that the first sliding surface of the first guide and the second sliding surface of the second guide extend in a helical fashion, and in that at least one of said first and second guides (5, 6) is movable about an axis of rotation transversal to the feeding line, said folding apparatus comprising an adjusting system for a relative position of the longitudinal edges (100a, 100b) of the continuous web once it has been folded, said adjusting system comprising at least one position sensor for checking a relative position of the longitudinal edges (100a, 100b) of the continuous web once it has been folded, at least one actuator (8, 9) connected to the first or to the second guide (5, 6) for moving it about the axis of rotation, a computerised control unit in communication with the position sensor and said actuator (8, 9) and configured for moving, by means of said actuator (8, 9) said first or second guide (5, 6) about the axis of rotation depending on a significant piece of information about the relative position of said edges (100a, 100b) as received from the position sensor. said folding apparatus comprising a folding section comprising a contact unit for the continuous web extending along the feeding line of the continuous web and defining the folding line; a first guide and a second guide which are positioned on opposite sides of the contact unit and respectively having a first sliding surface for the continuous web and a second sliding surface for the continuous web, wherein the first sliding surface of the first guide and the second sliding surface of the second guide extend along said feeding line, they each have a respective infeed section (51, 61), where the web is not folded, and a respective outfeed section (52, 62), positioned downstream of the respective infeed section (51, 61) according to a web feeding direction, where the continuous web is folded in two and has the first portion and the second portion set at an angle to each other, the infeed sections (51, 61) of the first and the second sliding surfaces being substantially coplanar the outfeed section of the first sliding surface and the outfeed section of the second sliding surface being transversal, preferably orthogonal, to the respective infeed sections (51, 61) and at least partly converging in the feeding direction of the continuous web, characterised in that the first sliding surface of the first guide and the second sliding surface of the second guide extend in a helical fashion, and in that at least one of said first and second guides (5, 6) is movable about an axis of rotation transversal to the feeding line, said folding apparatus comprising an adjusting system for a relative position of the longitudinal edges (100a, 100b) of the continuous web once it has been folded, said adjusting system comprising at least one position sensor for checking a relative position of the longitudinal edges (100a, 100b) of the continuous web once it has been folded, at least one actuator (8, 9) connected to the first or to the second guide (5, 6) for moving it about the axis of rotation, a computerised control unit in communication with the position sensor and said actuator (8, 9) and configured for moving, by means of said actuator (8, 9) said first or second guide (5, 6) about the axis of rotation depending on a significant piece of information about the relative position of said edges (100a, 100b) as received from the position sensor.