Abstract: A defective-portion marking method and defective-portion marking apparatus which can put a mark all around a long body (1), ensure easy removal of the mark, and eliminate the need for securely joining both ends of a line-like elastic body (2′) into a ring shape. A long elastic body (2) supplied from an elastic-body feeding mechanism (6) is held by a pair of pinchers (51), and as the pinchers are turned by a rotary mechanism (52), the long elastic body is wound on a holder (3). Then, the contact pin (41) of an entwining mechanism (4) moves forward to entwine the long elastic body, which is cut to the line-like elastic body by a cutter (516) provided on one of the pinchers. The contact pin moves further to free the line-like elastic body from the holder so that the line-like elastic body is wound around the long body at a defective portion or in a vicinity thereof due to its own elasticity.

Abstract: A device for marking an elongate material moving along a longitudinal path includes a support with an opening therein for the elongate material to pass through, a holding/releasing mechanism on the support for expanding and releasing an elastic ring onto the elongate material, the holding/releasing mechanism including drive means for releasing the ring, and a defect detection sensor disposed upstream of the holding/releasing mechanism for activating the drive means to release the elastic ring onto the elongated material when a defect is detected therein.