a 39 of the bobbin case member 6 39 with the result that the small diameter portion e of the retaining member 7 39 forms a clearance which extends from outside to the recess c 39 for smoothly passing an upper thread loop 13 therethrough after the loop 13 had entered the recess c 39 through the clearance the retaining member 7 39 turns counterclockwise shifting the acting side face b 39 of the member 7 39 to the left side of the recess c 39 in the bobbin case member 6 39 to open the recess c 39 toward the direction in which the loop 13 is to be passed thus the loop 13 is smoothly released from the recess c 39 with a further rotation of the outer shuttle member the retaining member 7 39 continues the above circular arc motion with the acting side face b 39 in contact with the side wall a 39 of the inner shuttle member 6 39 at all times in this way the circular arc motion of the acting side face of the retaining member along the contact face of the bobbin case member namely the side wall thereof assures smooth passage of the upper thread loop during the circular arc motion the acting side face of the retaining member is in contact with the same side face of the inner shuttle member namely the side wall thereof to prevent the rotation of the inner shuttle member with the construction described above in detail the device of this invention for use in a horizontally fully rotatable shuttle for retaining the inner.