The purposes of the research were to find out the clothing construction factors of the mechanical industry working clothes by analyzing the working clothes supplied to 5 subject companies; and to suggest the optimized sewing conditions and the seam strength and elongation experimental data according to the clothing material and seam types implied to the working clothes collected. The fabric types and trimmings used for the mechanical manufacturing working clothes were Polyester/Cotton(65/35%), Polyester/Rayon(65/35%), Cotton(100%); and linings, interlining, various fastenings etc. 2 stitch types, i.e. lock and two-thread chain stitches were applied to the construction of the flat, lap felled, French, superimposed, lapped and bound seams for the seam strength and elongation experiment. The results derived from the experiment were as follows. (1) The seam strength results according to the seam types were high in the order of lap felled>lapped>flat, superimposed and French seams. (2) Considering the features of the seam construction, as the number of fabric layers at the seam line increased the seam strength also increased. (3) Apart from the highest seam strength from the experiment using the net lining with the main fabric, the seam construction consisting of two fabric layers with the interlining showed relatively high seam strength results. (4) The seam elongations according to the stitch types were high in the order of two-thread chain>lock stitches.