To provide a fluff laying device for automatic winder capable of completing ballooning of spun yarn due to swirl flow within a yarn passage.

In a fluff laying device 1 having an opening part for yarn insertion which extends and opens in a shaft center direction of a yarn passage 8 on which swirl flow acts, a cover member 29 operable and closable for the opening part for yarn insertion is provided. When the cover member 29 is opened by revolving motion of a revolving body 26, yarn can be introduced into the yarn passage 8 via the opening part for yarn insertion. When the cover member 29 is closed by revolving motion of the revolving body 26, leakage from a side surface of swirl flow within the yarn passage 8 is eliminated.