To provide a needle width adjusting mechanism capable of adjusting and changing the bridle width of a sewing thread.

The binding machine has a needle bar 5 with a needle at the tip disposed at one end of an arm 3, and guiding thread loopers 11 and 12, a looper spreader 13, a thread tying mechanism 14 and a thread cutting mechanism 18 are disposed under a needle plate 10. A sewn object holder 19 consisting of a presser plate 23 and a receiving plate 22 is disposed along the upper surface of the needle plate 10 in such a way as can be reciprocated and oscillated. The groove width of long needle insertion holes 25 and 26 formed on the presser plate 23 and the receiving plate 22 respectively is formed larger than the width of parallel movement of the needle bar 5. The reciprocating oscillation of the sewn object holder 19 is interlocked with the lifting movement of the needle bar 5.