Social service is considered as an effective policy alternative for new social risk in Korean society. The concept and theoretical background of social service should be discussed for better social service policy. This paper tries to construct the conceptual framework and characteristics of social service. Concept of social service is classified into three categories, or broad, narrower, and narrowest. Social service has characteristics of quasi-public goods which has partially rivalry and partially exclusion. Interdisciplinary approach is essential for establishing social service paradigm. I hope that this paper become a clue for activating discussions on social service.