PURPOSE: To set a freely sewing margin by continuously sliding a chuck of cloth in a sewing direction Y, sequentially feeding it at a pitch designated in a direction X, placing a paper stencil at a rotatably symmetrical positions of 180 degrees at the neutral point of a needle position and a photoelectric sensor as a center, and controlling sewing according to the detection of the stencil by the sensor.

CONSTITUTION: Cloth is grasped by chucks 3, 4, a distance between X guide bars 5 and 6 is extended, and a paper stencil B of sewing margin is placed on a paper stencil base 10. In this case, the stencil is disposed at a rotatably symmetrical positions of 180 degrees to the neutral point E of a needle position 2 and a photoelectric sensor 9 to dispose a starting point at an equal distance D from the position 2 to a sew starting point C in a direction Y of the sensor 9. Thereafter, the bars 5, 6 are slid in a sewing direction along a Y guide bar 7. When the sensor 9 detects a starting point D of the stencil B, a sewing machine is stopped, the bars 5, 6 are reset to home positions, and the chucks 3, 4 are sequentially fed at one pitch in the direction X. Thus, the shape of the stencil is detected in the directions Y, X to realize the sewing margin as the shape.