To prevent occurrence of skip stitch failure by closely contacting up and down two sewing threads positioned in the upside of a thread handier when halfway parts of the two sewing threads linked between cloth and a louver are collected by a thread handler and withdrawing them from the reciprocating passage of the needle.

When the sewing needle is descending, this thread handier 10 to move for-/back-ward in the A-B direction shown by the arrow mark proceeds to the A-direction to hang and draw halfway parts of a two threads (loop parts) 5a, 5b linked between cloth and a louver 4 toward the side of the descending position of a sewing needle 1 and, when the sewing needle is ascending, the thread handier 10 recedes. The string handier part 11 is formed opening in an almost V-shape in the direction to collect the sewing thread 5a, 5b on the tip end part of the sewing needle 1 and a sewing thread inserting part 12 is formed on the central part of the thread collector 11. Skip stitch failure by proceeding the sewing needle 1 in between the sewing threads 5a, and 5b is prevented by bringing the halfway parts of the sewing threads 5a, 5b into a close contact condition.