To provide a grommet which can surely determine completion of a mounting of the grommet.SOLUTION: In a nearly disc-like disc part 20 mounted over a panel hole 210 in a hole penetration direction, an insertion tip end part 40 having a diameter larger than an insertion cylinder part 10 and a diameter smaller than the panel hole 210, a taper part 50 gradually expanding the diameter until an expansion diameter part 51 having a diameter one size larger than that of the panel hole 210 from the insertion tip end part 40, a diameter-reduced part 60 in which a burring 211 is arranged in a mounting state, and a large diameter part 70 arranged on an insertion rear end side from a vehicle body panel 200 in the mounting state are arranged in this order toward the insertion rear end side from the insertion tip end side. In the mounting state, a contact rib 62 projected to a diameter outside is provided to the diameter-reduced part 60 so as to be contacted to an inner peripheral surface of the burring 211. The contact rib 62 has a cross-sectional chevron shape of which a cross-sectional shape along an insertion direction X is projected to a radial outside.SELECTED DRAWING: Figure 4