A grommet is provided which can reduce an insertion load without decreasing a disengagement load of an inserting member. The inserting member, having a leg portion and a head portion formed by increasing the diameter of a tip end of the leg portion, is inserted from one end side of a body portion of the grommet into an insertion hole and attached to an inserted member with the grommet interposed. On the one end side from a groove portion formed in an outer circumferential surface of the body portion, a diameter of the insertion hole is equal to or larger than a diameter of the head portion. On the other end side from the groove portion, the grommet has a small diameter portion in which a diameter of the insertion hole is smaller than the diameter of the head portion and is equal to or larger than a diameter of the leg portion.