The utility model provides a copper wire winding device of an automatic welding machine and belongs to the technical field of metal can making. The copper wire winding device of the automatic welding machine comprises a rack, a copper wire coil, wire feeding roller shafts, winding shafts, a tension adjusting device and an unwinding shaft. The winding shafts are arranged between the wire feeding roller shafts and the unwinding shaft in a staggered mode, and the tension adjusting device is arranged between two of the winding shafts. The tension adjusting device comprises a tensioning rolling wheel, a tension adjusting shaft, an end cover, adjusting nuts and an adjusting plate. The adjusting plate is fixed to the rack, the adjusting plate and the rack are provided with same U-type grooves which are through in the front and back direction, threads are arranged on the tension adjusting shaft, a mounting base is arranged at one end of the tension adjusting shaft, the tension adjusting shaft is perpendicularly fixed to the rack and the adjusting plate through the adjusting nuts, the adjusting nuts are located at the two ends of the rack and the adjusting plate, and the tension rolling wheel is rotatably arranged on the portion, at one end of the tension adjusting shaft, of the mounting base and axially fixed through the end cover. Through the copper wire winding device of the automatic welding machine, the copper wire winding tension of the automatic welding machine can be adjusted, regular welding joints are guaranteed, and the quality of can bodies is improved.