A spinning unit comprising: a drafting device comprising: a plurality of roller pairs (14, 15, 16, 17) adapted to draft a fiber bundle, each roller pair (14, 15, 16, 17) including a driver roller (14a, 15a, 16a, 17a) and a driven roller (14b, 15b, 16b, 17b) adapted to rotate following rotation of the driver roller (14a, 15a, 16a, 17a); a stepping motor (M14, M15) adapted to rotationally drive the driver roller (14a, 15a) of at least one roller pair (14, 15) among the roller pairs (14, 15, 16, 17); a receiving section adapted to receive setting of a drafting condition relating to the fiber bundle to be drafted by the roller pairs (14, 15, 16, 17); and a control section adapted to control an operation of the stepping motor (M14, M15) by changing at least one among a magnitude of an electric current applied to the stepping motor (M14, M15), an excitation mode of the stepping motor (M14, M15), and a frequency of a pulse signal input into the stepping motor (M14, M15) such that drafting performed by the roller pairs (14, 15, 16, 17) is within a range that satisfies the drafting condition received by the receiving section; a spinning device adapted to apply a twist to the fiber bundle to form a yarn; a winding device adapted to wind the yarn to form a package; and a yarn monitoring device adapted to monitor the yarn, wherein the control section is adapted to adjust the operation of the stepping motor (M14, M15) when abnormality in the yarn is detected by the yarn monitoring device or when winding of the yarn by the winding device is in suspended state, characterized in that the control section is adapted to adjust the operation of the stepping motor (M14, M15) such that periodic unevenness having a frequency corresponding to a resonance frequency of the stepping motor (M14, M15) is not detected by the yarn monitoring device. a drafting device comprising: a plurality of roller pairs (14, 15, 16, 17) adapted to draft a fiber bundle, each roller pair (14, 15, 16, 17) including a driver roller (14a, 15a, 16a, 17a) and a driven roller (14b, 15b, 16b, 17b) adapted to rotate following rotation of the driver roller (14a, 15a, 16a, 17a); a stepping motor (M14, M15) adapted to rotationally drive the driver roller (14a, 15a) of at least one roller pair (14, 15) among the roller pairs (14, 15, 16, 17); a receiving section adapted to receive setting of a drafting condition relating to the fiber bundle to be drafted by the roller pairs (14, 15, 16, 17); and a control section adapted to control an operation of the stepping motor (M14, M15) by changing at least one among a magnitude of an electric current applied to the stepping motor (M14, M15), an excitation mode of the stepping motor (M14, M15), and a frequency of a pulse signal input into the stepping motor (M14, M15) such that drafting performed by the roller pairs (14, 15, 16, 17) is within a range that satisfies the drafting condition received by the receiving section; a plurality of roller pairs (14, 15, 16, 17) adapted to draft a fiber bundle, each roller pair (14, 15, 16, 17) including a driver roller (14a, 15a, 16a, 17a) and a driven roller (14b, 15b, 16b, 17b) adapted to rotate following rotation of the driver roller (14a, 15a, 16a, 17a); a stepping motor (M14, M15) adapted to rotationally drive the driver roller (14a, 15a) of at least one roller pair (14, 15) among the roller pairs (14, 15, 16, 17); a receiving section adapted to receive setting of a drafting condition relating to the fiber bundle to be drafted by the roller pairs (14, 15, 16, 17); and a control section adapted to control an operation of the stepping motor (M14, M15) by changing at least one among a magnitude of an electric current applied to the stepping motor (M14, M15), an excitation mode of the stepping motor (M14, M15), and a frequency of a pulse signal input into the stepping motor (M14, M15) such that drafting performed by the roller pairs (14, 15, 16, 17) is within a range that satisfies the drafting condition received by the receiving section; a spinning device adapted to apply a twist to the fiber bundle to form a yarn; a winding device adapted to wind the yarn to form a package; and a yarn monitoring device adapted to monitor the yarn, wherein the control section is adapted to adjust the operation of the stepping motor (M14, M15) when abnormality in the yarn is detected by the yarn monitoring device or when winding of the yarn by the winding device is in suspended state, characterized in that the control section is adapted to adjust the operation of the stepping motor (M14, M15) such that periodic unevenness having a frequency corresponding to a resonance frequency of the stepping motor (M14, M15) is not detected by the yarn monitoring device.