Six Sigma methodology has been used commonly in the manufacturing sector to eliminate the quantity of defects, however, recently years has been incorporated to the health sector to increase quality standard of safe and effective patient care. Six Sigma methodology helps hospitals to get at the root causes for variation and errors, and put sustainable improvements in place. This study focused on implementing Six Sigma model DMAIC (Define, Measure, Analyze, Improve, and Control) Roadmap and tools to get a solution to reduce waiting times at Okayama University Hospital. The research focused its attention on five factors to conduct the analysis. These factors are number of patients in the morning, number of patients in the afternoon. number of Doctors. service time. and number of staff from Monday to Friday. Factors were examined by performing a DOE (Design of Experiment) to analyze the impact of each factor on the waiting time. To optimize the result DOE were used to determine important factors and to find the optimum waiting times setting in the research.