The purpose of this study is to develop the reputation index for Korean government agencies and evaluate the characteristics and importance of the reputation index for government agencies. The government agency's reputation index development went through three stages to refine the index and secure reliability and validity. In the first stage, systematic literature reveiws on the reputation were done and the content validity was examined through in-depth expert interviews. In the second stage, a survey was conducted for the general public. Statistical analysis for the reliability and validity of the newly formed governmental repuration index were performed through confirmatory factor analysis and structural equation model analysis. In the third stage, the government agency's reputation index was applied to the Ministry of Patriots and Veterans Affairs as part of confirming predictive validity. Through these steps, it was confirmed that the government agency's reputation index is composed of four factors: vision, fairness, ability, and emotion. The vision, the fairness, and the ability factors consisted of 4 indicators, and the emotion factor consisted of 3 indicators. In particular, the vision and the fairness factors are crucial to the reputation of government agencies, and good leadership was found to be included in the fairness factors. In addition, the reputation of government agencies appears to have a positive effect on government trust and policy support, and these results demonstrate the effectiveness of reputation management for the governmental trust and policy support. This study has academic significance in that it has broadened the realm of reputation research by developing an index that can be applied as a standardized indicator in the reputation of government agencies. Futher studies on the evaluation of the government reputation would be necessary to secure the robustness of the newly developed index.