Many software companies are introducing the CMMI and managing a Quality Management Office (QMO) to strengthen organizational capacity and improve organizational processes. But, some of them are usually unable to make effective operation of a QMO. This is because quality management processes has been defined based on the process requirements only without considering the correlation between the SPs and GPs defined in CMMI support category. In this study, it surveys the correlations between SPs and GPs in CMMI support category, the correlations were confirmed through the chi-square independence test, and derived improvement plans in the organization's quality management process. This improvement plans were applied to the QMO operating in a small and medium-sized software company. Then it was confirmed that the performance of quality management improved.