To provide a grommet easily attached in a hole of a partition wall.

The rubber-made grommet is provided with a small-diameter cylinder portion 13 to which a wire harness W is inserted, a large-diameter cylindrical portion 15 having a diameter larger than that of the portion 13, a coupling cylindrical portion 17 for coupling the small-diameter cylindrical portion to the large-diameter cylindrical portion, a small-diameter flange portion 19 and a large-diameter flange portion 21 formed on the external circumference of the large-diameter cylindrical portion 15, and a fitting groove 23 formed between the small- and large-diameter flange portions. In the grommet, an internal circumferential groove 25 is formed on a position corresponding to the inside of the small-diameter flange portion 19 of the internal circumferential surface of the large-diameter cylindrical portion 15, and a plurality of leading pieces 27 to be led outside from an edge opposite to the large-diameter flange portion 21 of the internal circumferential groove 25 through the inside of the large-diameter cylindrical portion 15. When the leading pieces 27 are pulled in a leading direction, the small-diameter flange portion 19 is fell down in a direction opposite to the large-diameter flange portion 21 and reduced in diameter, so as to be inserted into a hole H of a partition wall K. When the flange portion 19 is released from the pulled state, the initial state is restored.