This research applied Six Sigma method to the improvement of production manufacturing process and attempt to improve production manufacturing process and move up the quality of production. In this research, firstly, the manufacturing process of case company is analyzed. The managers of case company were interviewed in order to find the course of making ill-quality product on manufacturing process. And then, the DMAIC execution steps of Six Sigma are applied to improve the manufacturing process. According to the investigation results, the proposed method can effectively reduce the rate of negligence arisen from human error from 5.5% down to 1.6%, and increase the overall quality of production manufacture of case company.