PURPOSE: To perform compacting and to advantageously transmit force between a driving device and an output shaft in a blind stitch sewing machine.

CONSTITUTION: This sewing machine is provided with sewing material moving devices 7 and 8 for advancing a sewing material stepwise and a drive shaft 10 turned back and forth so as to intermittently displace them. The drive shaft 10 is provided with a drive crank 32 projected in a radial direction, the drive crank 32 is connected to an output crank 35 by a link bar 34 of equal length and the output crank 35 is freely turnably supported on a base 36 around a shaft parallel to the drive shaft 10. The base 36 is freely turnably supported on an output shaft 11 cooperating with the sewing material moving devices 7 and 8 and is adjustable by the means of a seam length adjustment device 33. The output shaft 11 is also parallel to the drive shaft 10 and is driven by the output crank 35 through a driving device 33 equipped with the base 36.