The case study method is used in this research to examine the case company’s post-M&A performance and key success factor (KSF) in M&A. The results show that there are ways a company can enhance its overall performance, for example by improving asset utilization efficiency and financial structure in M&A activities. The KSF for M&A include effective integration of human resources, rapid building an information platform, sharing resources such as R&D, improving manufacturing techniques, distribution channels etc. It is shown that synergy in M&A therefore results from management rather than from M&A itself.