Abstract: Disclosed is a bobbin case of a rotary shuttle device for a sewing machine, in which an under thread pulled out of a bobbin is continuously and stably supplied to a sewing region.

Abstract: A bobbin for a sewing machine which is rotatably disposed in a rotary shell device of the machine to supply and under thread when performing a sewing operation, comprises of winding shaft separately inserted onto a fixed shaft of the rotary shuttle and on which the under thread is substantially wound, a first flange integrally formed at one end of the winding shaft, a second flange integrally formed at the other end of the winding shaft, and a partition flange forming a first winding portion between the first flange and the partition flange and forming a second winding portion between the second flange and the partition flange, a plurality of saw-toothed protrusions being formed at an entire outer circumference of the partition flange, and the protrusions having a linear sidewall that is oriented in a radial direction of the partition flange.