To enhance waterproofing of the connecting part of a connector in a panel hole and the workability of connection thereof.

A waterproof grommet 9 mounted on a wire harness 7, covering the connector 3 of a unit part and the connector of a wire harness is fixed closely to a panel 1 by means of bolts 10, 11. A bolt 12 for fixing the waterproof grommet 9 tentatively at a position displaced from the normal fixing position is erected on the panel 1. The bolts 10, 11 for fixing the waterproof grommet 9 at a normal position are erected on the panel 1 and, with the bolt 10 as a fulcrum, the waterproof grommet is allowed to turn to the bolt 12 for tentative fixing. The wire harness leading-out part 17 of the waterproof grommet 9 is disposed nearer to the bolt 10. The waterproof grommet 9 is formed with an bellows 15 extendable in such a direction that the connector fitting is released and, while the bellows is compressed, the connector 8 of the wire harness 7 is exposed completely.