A door harness attaching structure includes: an opening provided on an inner panel of a hinge-open/close-type door; and a hole provided on an end wall at the hinge side of the inner panel. The opening is composed of a large main opening covered by a panel unit of a door module and a small sub opening continued to the main opening, notched toward the hole for attaching a grommet and covered by a cover member. A wiring harness of the door module includes: a harness portion projecting from the panel unit; and the grommet provided at a tip end of the harness portion and attached through the hole.