A portable electromagnetic induction welding device for joining tapes of adherends in electrically conductive composite materials with a polymeric matrix, said device comprising: - a base facing a work surface, in turn designed to receive said tapes of adherends to be joined or defined by at least one tape of adherend already positioned to receive one or more other tapes of adherends; - an operating head receiving one tape of adherend at a time and movable with respect to said base along at least a first movement line parallel to said work surface for stretching the received tape of adherend on the work surface; - a motorized arm connecting said operating head to said base and selectively activatable to impart movements to the operating head parallel to said first movement line and also parallel to at least a second movement line transversal to the first movement line and parallel to said work surface; and - feeding means selectively activatable to feed one tape of adherend at a time to said operating head and connected to the operating head; wherein said operating head comprises: - at least one pressure roller; and - at least one inductor selectively energized in use to generate an electromagnetic field suitable for inducing parasitic electric currents in said tapes of overlapped adherends so as to produce, by the Joule effect, the local fusion of polymeric matrices in contact with each other of the tapes of adherends; characterized in that said operating head also comprises at least one positioning roller receiving one tape of adherend at a time from said feeding means; in that said at least one pressure roller is spaced from and aligned with said positioning roller along said first movement line; and in that said at least one inductor is interposed between said positioning roller and said pressure roller with reference to said first movement line. - a base facing a work surface, in turn designed to receive said tapes of adherends to be joined or defined by at least one tape of adherend already positioned to receive one or more other tapes of adherends; - an operating head receiving one tape of adherend at a time and movable with respect to said base along at least a first movement line parallel to said work surface for stretching the received tape of adherend on the work surface; - a motorized arm connecting said operating head to said base and selectively activatable to impart movements to the operating head parallel to said first movement line and also parallel to at least a second movement line transversal to the first movement line and parallel to said work surface; and - feeding means selectively activatable to feed one tape of adherend at a time to said operating head and connected to the operating head; wherein said operating head comprises: - at least one pressure roller; and - at least one inductor selectively energized in use to generate an electromagnetic field suitable for inducing parasitic electric currents in said tapes of overlapped adherends so as to produce, by the Joule effect, the local fusion of polymeric matrices in contact with each other of the tapes of adherends; - at least one pressure roller; and - at least one inductor selectively energized in use to generate an electromagnetic field suitable for inducing parasitic electric currents in said tapes of overlapped adherends so as to produce, by the Joule effect, the local fusion of polymeric matrices in contact with each other of the tapes of adherends; characterized in that said operating head also comprises at least one positioning roller receiving one tape of adherend at a time from said feeding means; in that said at least one pressure roller is spaced from and aligned with said positioning roller along said first movement line; and in that said at least one inductor is interposed between said positioning roller and said pressure roller with reference to said first movement line.