The purpose of the study was to explore how adult instructor understand global citizenship education, how their life changed through global citizenship education teaching experience and what the experience means to the participants. To achieve the research purpose, qualitative content analysis was used. The research participants were 6 adults who are teaching global citizenship education for over 2 years at school, civic group and NGO for international relief. The results of the study are as follows: First, the research participants understood global citizenship education as that forms a wide view to see the world beyond one country and teaches the value of coexistence. They also realized there is a great distance between theory and practice due to limitation of Korean education system. Second, global citizenship education teaching experience became a momentum to develop the ability to choose and act for the life toward a global citizen. Third, the participants transformed their values through .the teaching experience of the global citizenship education. They turned themselves into a teacher who challenges educational obstacles and had an opportunity to form a vision for career and life through global citizenship education teaching experience.