An induction pre-heating and butt welding device for adjacent edges (2, 3) to be joined of at least one element to be welded, of the type comprising an induction pre- heating head of the adjacent edges, the pre-heating head having a first inductor, a welding head arranged in tandem with respect to the pre-heating head, immediately downstream of the pre-heating head, with respect to a welding direction along which, in use, the pre- heating and welding heads are moved according to a welding trajectory; characterized in that the pre-heating head comprises, in combination: i)- a sliding block supporting structure shaped as a box shaped body open on at least one first face which, in use, faces the at least one element and the adjacent edges (2, 3) and adapted to move over the edges (2, 3) to be welded, parallel thereto; ii)- the first inductor lying in a first plane, which is parallel to a plane containing, or passing through, the edges (2, 3) to be welded, which is integrally supported by the support structure at a predetermined distance from the edges to be welded and which is housed within the thickness of said sliding block supporting structure on the side of a first face thereof; and iii)- a second inductor lying in a second plane, perpendicular to the first plane and integrally supported by the sliding block supporting structure in cantilever fashion out from said first face of sliding block supporting structure and across sliding block supporting structure itself, so as to be in use interposed between the edges (2, 3) to be welded and arranged at a predetermined distance from the first inductor, wherein the inductors (9, 14) are provided, in use, with corresponding electrical power converters (29, 30) which are independent from each other; iv)- the sliding block supporting structure being provided with centering means with respect to the edges (2, 3) to be welded, adapted to keep the second inductor, in use, constantly equally spaced apart from both edges to be welded and the first inductor constantly centered over the edges to be welded (2,3). i)- a sliding block supporting structure shaped as a box shaped body open on at least one first face which, in use, faces the at least one element and the adjacent edges (2, 3) and adapted to move over the edges (2, 3) to be welded, parallel thereto; ii)- the first inductor lying in a first plane, which is parallel to a plane containing, or passing through, the edges (2, 3) to be welded, which is integrally supported by the support structure at a predetermined distance from the edges to be welded and which is housed within the thickness of said sliding block supporting structure on the side of a first face thereof; and iii)- a second inductor lying in a second plane, perpendicular to the first plane and integrally supported by the sliding block supporting structure in cantilever fashion out from said first face of sliding block supporting structure and across sliding block supporting structure itself, so as to be in use interposed between the edges (2, 3) to be welded and arranged at a predetermined distance from the first inductor, wherein the inductors (9, 14) are provided, in use, with corresponding electrical power converters (29, 30) which are independent from each other; iv)- the sliding block supporting structure being provided with centering means with respect to the edges (2, 3) to be welded, adapted to keep the second inductor, in use, constantly equally spaced apart from both edges to be welded and the first inductor constantly centered over the edges to be welded (2,3).