A first grommet 11 includes a ring-shaped seal portion 15 into which a peripheral edge of an attachment hole Pa is fit, and a joining piece 23 serving as a first joining portion. A second grommet 12 includes a holding portion 33 serving as a second joining portion that is joined to the joining piece 23. The seal portion 15 includes a brim portion 21 serving as a first flange portion that is engaged with a side surface Pc of a vehicle body panel P, and a lip portion 22 serving as a second flange portion that is engaged with a side surface Pb of the vehicle body panel P. Also, the joining piece 23 is formed on the inner side in the radial direction of the lip portion 22.