A rotary looptaker includes a looptaker body rotatable about a vertical axis and a bobbin case restrained from rotary motion with the looptaker body. A plurality of annular protrusions are provided on a flange of the bobbin case so as to extend in a circumferential direction of the bobbin case and are in engagement with a flat surface formed on a raceway of the looptaker body. When the looptaker body is rotated, the bobbin case slides relative to the looptaker body through a very small contact area between the annular protrusions and the flat surface, thus reducing sliding friction between the looptaker body and the bobbin case. Accordingly, noise and vibration are decreased when a rotation restraining projection of the bobbin case contacts a restraint element secured to a machine frame.