To provide a grommet having a sound insulation performance improved by sealing an air space.

The grommet comprising an inner cylinder through which a wire harness is inserted and an outer cylinder formed by projecting a portion of the inner cylinder from an outer periphery thereof in a diameter direction and then folding the portion so as to ensure the air space for sound insulation performance between the outer cylinder and the inner cylinder, the outer cylinder extending in an axial direction and being provided with an annular vehicle engagement recess part on one end thereof in the axial direction, and the inner cylinder and the outer cylinder are made into one body with rubber or elastomer. The inner cylinder projects away from the other end of the outer cylinder, an opening for the air space for sound insulation performance is provided between an outer periphery of the inner cylinder and the other end of the outer cylinder, the opening is to be closed by winding an adhesive tape from an outer periphery of the outer cylinder to the outer periphery of the inner cylinder, and the outer cylinder to be wound by the adhesive tape has an area provided with a plurality of creases in a circumferential direction. Widths of these creases in the circumferential direction are made gradually wider toward an edge of the outer cylinder in the axial direction, such that the opening is closed by folding the creases of the outer cylinder and winding the adhesive tape in a squeezing manner.