PURPOSE: To improve the sewing performance of the sewing machine for lock stitch by preventing incidental looping, looping or cut of a thread by smoothly passing the thread through the shuttle in the case of performing sewing work while using the sewing machine for lock stitch provided with the shuttle.

CONSTITUTION: On the outer peripheral face of a rotating hook bobbin case holder 31 provided at a vertical fully rotary shuttle 30, a track line 38 is extended in its peripheral direction and formed with wide width from the axial center part of the outer peripheral face to a bottom part 37. On the inner peripheral face of a rotating hook 34, on the other hand, a wide track groove, to which the track line 38 is fitted, is formed while being extended in the peripheral direction.