This paper proposes an analysis methodology that enables the establishment of improved customer satisfaction via decision support system using customer satisfaction index data and customer database of a company. The proposed methodology establishes rational future goal of a company by applying DEA, finds potential customers which correspond to demographic features of the previous target group, and improve quality factors which distinguish the quality-satisfaction-group from the quality-dissatisfaction-group through the use of machine learning tools, SOM and C4.5. Finally, we illustrate the effectiveness of our research methodology using actual data of a camera company.