The concept of Communities of Practice (CoPs) has been highlighted as an effective method for knowledge sharing in Knowledge Management (KM) and strategically utilized by many organizations. Therefore, the need to diagnose knowledge sharing activities in CoPs has increased. Previous research on CoP strategies has generally suggested broad guidelines without diagnosing the current knowledge sharing status of individual CoPs. Furthermore, diagnosis methodologies are not connected to strategic direction and require too much time and effort to conduct regularly. The purpose of this paper is to develop a sustainable diagnosis framework for identifying knowledge sharing activities in CoPs using Social Network Analysis (SNA) and to suggest strategies for individual CoPs based on the proposed diagnosis framework. Finally, we apply the proposed diagnosis framework to an industry case.