To provide a grommet in which the waterproof performance of a panel fitting portion can be enhanced by preventing the elastic deformation of the panel fitting portion surely after panel mounting.

A grommet 10 is equipped with a cylindrical wire fitting portion 11 through which a wire harness W passes and to which the same is fitted, and an approximately elliptical cylinder-like panel fitting portion 13 which is fitted to the elliptical through hole of a panel in an elastically deformable manner. Therein, the linear portion P thickness of the abutting flange portion 16 of the panel fitting portion 13 is formed so as to be thicker than the thickness of a circular arc portion Q. The panel fitting portion 13 is formed of a guide slope portion 14 which is guided to the through hole of the panel, a fitting slit 15 which is fitted to the through hole, and the abutting flange portion 16 which abuts on the panel around the through hole. The thicknesses of a guide slope 14 tip portion 14a and the respective linear portions P of the abutting flange portion 16 are protrusevely formed so as to be thicker outward than the thicknesses of the respective circular arc portions Q, and the thicknesses of the linear portions P of the abutting flange portion 16 are protrusively formed so as to be further thicker inward than the thicknesses of the circular arc portions Q.