The International Astronomy Olympiad (IAO) was established by the Euro-Asian Astronomical Society in order to disseminate astronomical knowledge, promote international cooperation in astronomical education area and recognize the importance of astronomy in far-reaching field of science and human culture. The first IAO competition was held at the Special Astrophysical Observatory of the Russian Academy of Sciences located in the north Caucasus of Russia in 1996. Since then, it has been held every year. This paper describes the present status of the IAO main regulations regarding its operation and major results by year, related institutions, and organizations. We created a scientific inquiry framework to analyze past IAO problems in the recognitive aspect in order to measure levels of the scientific knowledges and the scientific thinking abilities. Through this analysis, we can understand the current status of the IAO, and examine the future direction of Korea Astronomy Olympiad. Also, we can make preparation for the IAO competition and the education of delegates.