PURPOSE: To reduce the waste cotton ratio and further fiber content in waste cotton, by lowering an auxiliary nipper in advancing the nipper body, and giving resistance to the top surface of a fiber bundle in front of a feed roll.

CONSTITUTION: A nipper device of a nipper body 6, moved forward and backward to detaching rolls 3, and having a fixed cushion plate 8 equipped with a nipper 10 provided movably up and down to the cushion plate 8, a feed roll 9 on the upstream side of the nipper 10, and an auxiliary nipper 16 provided movably up and down to the cushion plate 8 between the feed roll 9 and the nipper 10. A clearance holder 26 for leaving a space gauge between the auxiliary nipper 6 and the cushion plate 8 in lowering the auxiliary nipper 16 is provided.