PURPOSE: To automatically finish the neat seam by controlling the peripheral direction position of a rod needle by a control motor connected with a needle rod so that the flat plane of a flat needle is set always parallel to a thread traveling direction.

CONSTITUTION: When a workpiece is moved on an XY-table according to a pattern which is previously program-set, the revolution angle quantity for setting the flat plane of a flat needle in parallel to a thread traveling direction is instructed for a control motor 27 from a computer, and when the motor 27 turns by this revolution angle quantity, a rack 24 shifts to turn a cylindrical body 22 through the connecting rods 25 and 23, and a needle rod 2 turns by the angle demanded according to the program. Then, the flat needle 1 is lowered to pass the workpiece, and the flat needle 1 is turned to the peripheral direction position of the flat needle 1, and an upper thread is applied onto a lower thread by a kettle 11. Then, a revolution instruction in the demanded revolution angle quantity is sent into the control motor 27, and the needle rod 2 is turned, and the flat plane of the flat needle is set parallel to the thread traveling direction again, and the flat needle 1 is allowed to pass the workpiece and slip off.