To enable stop of a sewing arm at an accurate position in a simple structure without a positional correcting device, by connecting the output shaft and the slewing shaft by a link mechanism and transmitting the slewing angle of the slewing arm member to the slewing base at the double angle.

A slewing shaft member 2 and the output shaft 10 are arranged to axially separate from each other. The rotary movement of the output shaft 10 is transmitted to the slewing base through a transmitting shaft member 14 separated by a distance L and parallelly arranged and the first and second connection mechanisms 15, 16. The second projection 27 at the front end of the driven member 25 is fitted to the second long groove 26 of the slewing arm member 24 so as to freely slide and the first projection 22 at the front end of the driving arm member 20 is fitted in the first long groove 21 of the slewing wheel 18. The length L2 of the driven arm member 25 is made equal to L1 and the fitting position of the first projection 22 is arranged so as to bisect the distance L3 of the fitting position of the second projection 27 before and after the rotary movement of the driven arm 25 and the axial center of the intermittent shaft member 14. Since the slewing angle of the arm member 24 is transmitted to the slewing base at the double angle, the slewing angle of the arm member 24 can be reduced and the slewing base can be stopped at an accurate position.