The invention discloses a fiber treatment device linkable to a picker (1) or carding machine roller (2, 3, 4) including at least one regulating vane (17d) to compact a fiber layer (5) against a circumferential surface (9) of the roller (4) in order to limit its thickness and a compaction organ (19) positioned before the regulating vane (17d) in the rotation (v4) direction of the roller (4), wherein this compaction organ (19) compacts the fiber layer (5) and guides it towards the circumferential roller (4) surface (9) before the regulating vane (17d).