The study seeks to look into the differences in the use of apology speech act between South and North Korea. In order to do so, 9 sentences on apology speech act were constructed for a survey that was conducted with 74 South Koreans and 73 North Korean defectors. The surveys questions included the perception of apology speech act, the usage frequency, and the most frequently used expressions in apology speech act. The responses were investigated and compared. The results of the survey showed that North Koreans more negatively perceived the act of apology speech act to others compared to South Koreans. Moreover, when a specific situation was given, North Koreans were less likely to understand that an apology speech act was required in that situation. Furthermore, there was a large difference in understanding of one`s fault or pressure between North Korean and South Korean respondents. This was the cause for the differences in the situations where an apology speech act was given. Also, there was a difference in the expressions used by the South and North Koreans in giving and accepting apology speech act. The study demonstrated that there was a large difference on the perception of apology speech act itself between South and North Korean respondents. The differences in perception is the cause for the differences in situations and the expressions where an apology speech act is given. Moreover, this determines the course of action employed in order to maintain social relations when one`s fault harms the reputation of another. Therefore, instead of the linguistic differences, a way to bridge the differences in perception must come first. Though the study is limited in its size of the sample, it is expected that the results of the study will influence the ways of unifying language use between South and North Korea, and aid the adjustment of North Korean defectors in South Korea.