To sew a material fed into a machine by one or both of flat sewing and close sewing modes by selectively transmitting a driving power source to at least one of flat sewing and close sewing head assemblies and sewing the fed material by at least one of both head assemblies.

When a clutch assembly 17 is moved to a right side, the toothed inner part is engaged with the toothed outer surface of a shaft sleeve 7, the shaft sleeve 7 starts rotation and thus, a bent shaft 6 is also rotated and driving power is transmitted to the flat sewing head assembly. When the clutch assembly 17 is moved to a left side, a different part with spline is engaged with the part with the spline of a pulley 10 and the pulley 10 is rotated accompanying the rotation of the clutch assembly 17. Thus, the driving power is exerted to the close sewing head assembly. Also, when the clutch assembly 17 is positioned at a center position, both of the flat sewing head assembly and the close sewing head assembly are freely operatably engaged.