Apparatus for crimping fibers comprises a ring roller of a comparatively large diameter which rotates in one direction and an inscribed roller which contacts the inner surface of said ring roller and which rotates in the same direction at the same velocity as the ring roller while holding bundles of fibers to be crimped between the two rollers and side rings which are situated on both sides of the place of contact of the two rollers and which rotate in the same direction at the same velocity as these rollers, and by forming the surrounding of a stuffing box by said rollers and rings.