A spindle unit includes a swing mechanism fixed to a fixed frame, a support member swingably supported by the swing mechanism, a spindle main body and an electromagnetic brake supported by the support member. The spindle main body rotates integrally with a bobbin around which a yarn is wound. The electromagnetic brake applies a resistance to the rotating spindle main body. The swing mechanism includes a fixed attachment member fixed to the fixed frame, a swing shaft supported by the fixed attachment member, a spring, and a sensor. The spring applies a spring force to the support member in a direction opposite to a direction in which the support member swings by the tension of the yarn. The sensor detects the tilt amount of the support member when the support member swings.