The purpose of this study is to examine the impact of the traumatic incidents of North Korean refugees in North Korea and during the process of defection on their adaptation to South Korean society. And their complex post-traumatic stress disorder was selected as a noteworthy variable, as this study focused on how negative factors caused by their experience of traumatic incidents were manifested psychologically, and whether the complex post-traumatic stress disorder of North Korean refugees had any mediating effect on the relationship between their trauma experience and adaptation to South Korean society was analyzed. After a survey was conducted on the North Korean refugees who resided in Seoul and Gyeonggi Province, the collected data from 405 respondents were analyzed. The major findings of the study were as follows: First, the North Korean refugees' experience of traumatic incidents that was the independent variable was found to have exercised a negative influence on their complex post-traumatic stress disorder that was the mediator. Second, their experience of traumatic incidents was found to have exerted a negative influence on their social adaptation that was the dependent variable. Third, when their complex post-traumatic stress disorder was inputted in the relationship between experience of traumatic incidents and social adaptation, there was no more significant relationship between experience of traumatic incidents and social adaptation, and only complex post-traumatic stress disorder was found to have affected social adaptation significantly. Thus, it's found that the complex post-traumatic stress disorder of the North Korean refugees had a full mediating effect on the relationship between their experience of traumatic incidents and adaptation to South Korean society. Given the findings of the study, the kind of intervention that could facilitate the social adaptation of North Korean refugees was suggested.