For preventing clamping an elastic grommet main body at open/close, a waterproof grommet (25) has an elastic grommet main body (2) passing electric wires therethrough and a hold member (30) mounted on an outer surface of an intermediate portion in a lengthwise direction of the grommet main body. The hold member is mountable on a mounting part. The grommet main body (26) has a cylindrical portion (4) and bellows portions (2), (3) at the both side thereof. The hold member (30) is provided on the cylindrical portion. The hold member 30 includes a ring portion (14) and a holding portion (15) provided at the ring portion 14. The ring portion (14) is lockable and capable of being opened and closed.