A grommet body of a grommet includes: a large-diameter tubular portion; a first small-diameter tubular portion arranged on one side of a through-hole; and a second small-diameter tubular portion arranged on another side of the through-hole. The grommet body includes an umbrella-like sound insulation portion which covers the through-hole from another side, and the sound insulation portion is configured such that an abutting side surface is folded back in such a way as to face a radial outer side of the grommet body with a folded-back portion as a base point. The sound insulation portion in a state in which the abutting side surface is folded back in such a way as to face the radial outer side of the grommet body has a pleated shape, and an outer diameter of the sound insulation portion in this state is smaller than an inner diameter of the through-hole.