The purpose of this study is to improve effectiveness of Korea’s Official Development Assistance (ODA) provided to developing countries. To do this, we analyze the efficiency of ODA provided to 38 recipient countries by Korea through data envelope analysis method. The effects of four factors including population, GDP, economic decline and poverty, and external intervention on efficiency are also investigated by utilizing tobit regression analysis. As a result of the DEA efficiency analysis, it is found that the average efficiency score of the total is about 59%. By region, the average efficiency score of Asia, Africa, Central and South America, and the East and CIS (Commonwealth of Independent States) are about 42%, 68%, 70%, and 74%, respectively. It indicates that the Asian countries are inefficient compared to countries of the other regions. It is also found that factors of population, GDP, economic decline and poverty, and external intervention have statistically significant effects on efficiency at 0.01 significance level. In the case of the population, the higher the population of the recipient country, the more negative (-) effect is on the efficiency. The other factors such as GDP, economic decline and poverty, and external intervention have positive effects on the efficiency.