Considering the expansion of social media and its critical implication in crisis management research, this study aims to explore the exposure effect of CEO Twitters’ apology in crisis situation. With checking the basic effect of CEO Twitter’s apology in crisis situation, this study used 2 (organizational representative vs. individual) × 2 (rationally vs. emotionally appealed apology) experimental design to examine whether a CEO Twitter’s apology has an effect on public perceptions of crisis situation. Through analyzing 271 respondents’ data gathered from June 15 to 30 in 2011, the publics’ evaluation on crisis situation was positively influenced by the CEO’s Twitter apology itself, and the apology message which constructed in emotional appeal. However, any effect of apology subjects’ types was not found in the public perceptions about the given crisis. In conclusion, the results demonstrate that CEO twitting in crisis situation has a significant meaning as an organization’s crisis management tool, plays an important role for publics to accept the organizational apology messages, and increase the levels of trust on the organization. Therefore, integrating CEO twitting and apology message, this result gives a bottom-line how to develop the social media based crisis management in public relations research.