Purposes: The objective of this study is to analyze service design process of dental clinic preventive service by using 'Double Diamond Design Process' which is user-centered for improving dental clinic management efficiency. Methodology: We examine case study that dental clinic preventive service of local dental clinic. Following the double diamond design four steps(①discover, ②define, ③develop, ④deliver), we use suitable analytic tools in each steps. In discover step, we perform observation and desk research. Next, in define step, affinity diagram, user persona, and user journey map are performed. We then make service blueprint in develop step. Finally, in deliver step, virtual scenario and confirm some outputs which are based on results of former steps are suggested. Findings: As a result of this study, waiting and consulting phases turn out that these phases are in the most trouble than others. Users(patients) have lots of complain and dissatisfaction in these phases. These touch-points will have to be modified Practical Implication: After checking this study result, it could suggest improvement schemes. To apply these, we try to make some scenarios, and finally realize some outputs. Service design has arisen to strengthen the competitiveness by reflecting user's experience and needs. Especially, service design is not typical, it is so flexible that can apply to various situation and objects. We hope that result of this study is made good use for dental clinics in need.