An investigation made of fabric strength & elongation and the lock stitch seam strength & elongation by stitch density (N1.5; 26 stitches/3 cm, N2.0; 19 stitches/3 cm, N2.5; 14 stitches/3cm) depending on methods of. sample prepariation (angle variations of unseamed sample and overlapping way of seamed sample) It found maximum stitch density that results of the seam strength test was highist in each angle of bias. The results obstained were as follows: 1. As the results of fabric strength and elongation tests as a function of angle of bias, breaking strength were that warp and weft angles (0$^{circ}$, 90$^{circ}$) were much higher than bias angles (20$^{circ}$, 30$^{circ}$, 45$^{circ}$, 60$^{circ}$) . And otherwise breaking elongation were that 45$^{circ}$ angle of bias were highest and were that the warp & weft way were lower. 2. As the results of the seam strength tests by the stitch density under samples of same angles, the maximum stitch density were those; under 0$^{circ}$/0$^{circ}$, 60$^{circ}$/60$^{circ}$:F1, F2-N2.0, F3-N1.5, under 20$^{circ}$/20$^{circ}$, 30$^{circ}$/30$^{circ}$, 45$^{circ}$/45$^{circ}$: F1-N2.5, F2-N2.0, F3-N1.5, under 90$^{circ}$/90$^{circ}$: F1, F2, F3-N1.5. 3. As the results of the seam strength tests by the stitch density under samples of symmetry angles, the maximum stitch density were those; under 20$^{circ}$/-20$^{circ}$, 30$^{circ}$/-30$^{circ}$, 60$^{circ}$/-60$^{circ}$: F1, F3-N1.5, F2-N2.0, under 45$^{circ}$/-45$^{circ}$: F1, F2-N2.0, F3-N1.5.