PURPOSE: To easily execute efficient deep hemstitch sewing with high quality by turning a hem edge by the flow pressure of gas blown out from a gas blow out port, simultaneously, pressing cloth by a rectifying board, guiding the cloth to the guide surface of a hem turn width adjustment guide scale and determining a hemstitching margin.

CONSTITUTION: The hem is turned while guiding a material (h) to a guide blade 4 of a hemstitch margin adjustment scale 6 by the flow pressure of gas blown out from gas blow out ports (c), (d) and (e) of a hem turn presser 1. Simultaneously, the material (h) is exactly positioned to objective width while automatically correcting the material to a guide surface 12 of a turn width adjustment guide scale 5 in a state that the material is adhered to a hemstitch margin guide surface 14 by the gas pressure rectified by a rectifying board 11. The determined hemstitch margin is guided to a needle plate by the hem turn width adjustment guide scale 5 and a hemstitch line guide scale 2.