The garment industry, especially the knitted socks industry and the like, experienced a decline in production due to production defects that did not meet the target. The aim of this study was to analyze the factors causing the dominant fault, determine the proposed improvement, determine the sigma level of the socks defect by applying Six Sigma with the Define-Measure-Analyze-Improve-Control (DMAIC) approach. This study found that the factors causing the dominant stockings defect based on the Failure Models Effect Analysis (FMEA) analysis were unsuitable linking needles at 504 RPN, yarn hardness varied by 441 RPN, thread clumps in cutter 384 RPN, direct socks entering the plate is 294 RPN. The researcher proposes that improvement efforts are included in Key Performance Indicators (KPI) so that all forms of improvement can be documented and socialized to employees. To measure the sigma level before the repair of sigma 3.7017 and after the restoration of sigma 3.9614, there is an increase in the level of Sigma after the improvement of the quality of the single type socks 7%. Meanwhile, the percentage of Lonati Single Knitting defects fell from 11.08% to 5.54%.