Abstract: In a first production process, firstly, a flat corrugate tube 23 having a necessary length for wiring is prepared. Next, a grommet 25 and a protector 24 are assembled with the flat corrugate tube 23 at predetermined positions. In a second production process, high-voltage power lines 22 and low-voltage electric wires 27 are inserted into the flat corrugate tube 23 from the one opening 40 toward the other opening 41. In a third production process, ends of the high-voltage power lines 22 and the low-voltage electric wires 27 exposed from the one opening 40 and the other opening 41 of the flat corrugate tube 23 are treated. When the third production process is finished, the production of the wiring harness 21 is finished.