To enhance waterproof performance at the part for fixing a grommet in an automobile.

In a waterproof structure where a wire harness W/H is inserted through a grommet 10 comprising an enlarged part and a small diameter tubular part into a through hole made through a panel partitioning the outdoor side and the indoor side of an automobile and the grommet 10 is filled with a water stopping agent, the enlarged part of the with harness W/H is arranged at a part where a sheet-like water absorbing material 15 is wound spirally between wires (w) and bundled. Furthermore, a part 15a of the water absorbing material 15 is brought into contact with a water stopping layer 14 filling the enlarged part 11 while the other part 15b is projected outward from the water stopping layer 14 and exposed to the outer air so that the water absorbing material is not saturated.