An investigation was made of the angle of bias on the lower part of the armhole line of the back bodice and that on the lower part of the sleeve cap curve line by cap heights, and then it was made of the lock stitch seam strength and elongation on the matching angles, the stitch density (26 stitches/3cm, 19 stitches/3cm, 14 stitches/3cm, and the samples (a cotton fabric and two kinds of cotton mixed polyester fabric). The matching angles of the machine-sewed samples are $30^{circ}/-30^{circ}$, $30^{circ}/-45^{circ}$, $45^{circ}/-45^{circ}$ and $60^{circ}/-60^{circ}$ by the analysis of the angles of bias on the lower part of the armhole seam. In view of the results of the seam strength and elongation, the reasonable sewing condition of the lower part of the armhole seam was 19 stitches/3cm.