Textile machinery and periodic unevenness detecting method therein

When a periodic unevenness of a drafted fiber bundle (8) is detected, a draft ratio in a draft device (7) is changed. Since a generation period of the periodic unevenness in the fiber bundle changes in accordance with a change in the draft ratio, a textile machinery detects the periodic unevenness under a plurality of different draft ratios, acquires the detection result, and inspects a change in the detection result. The periodic unevenness may be generated by a plurality of overlapped causes depending on generated positions of the periodic unevenness on the fiber bundle. In such a case, a position where the generation cause of the periodic unevenness may exist can be limited by changing the draft ratio and inspecting the change in the detection result.