The existence of eunuchs in Korean history has been found since the Silla period. However, the details of the Silla period’s eunuch are unknown. More details on the composition and role of the eunuch are confirmed in the Goryeo Dynasty. Previously Military Revolt(武臣政變), the eunuchs were kept in small numbers and played only a simple role in the palace. This is because during the reign of King Munjong, the number of eunuchs consisted of about 10 people and it was confirmed that only simple tasks were undertaken in the palace. Meanwhile, as the eunuch system was reorganized, the activity of eunuchs began to increase. The eunuch’s activity was expanded through the passing of King Yejong and Injong, and eunuch was involved in political problems or exerted political influence on the king. Expecially, eunuch was able to gain favor and power by actively participating in the policy of strengthening the royal authority of King Uijong. As Military Revolt took place, the political influence of eunuchs plummeted. This is because King Uijong was deposed and a large number of eunuchs were killed. In particular, negative perceptions of eunuchs prevailed as the actual situation of Uijong’s maladministration was highlighted. In this situation, King Myeongjong kept a certain distance from eunuch. However, as Lee Eui-min came to power, eunuch again emerged as a close ally of the king. But after Choi Chung-hun’s reign, the royal authority was reduced, and the activities of eunuchs declined again. With the political change taking place under the leadership of Kim Jun, the activities of eunuchs began to increase. In particular, eunuchs became a key aide to the king as he participated in the elimination of Kim Jun. Also, thanks to Mongol military power, the royal authority was restored, increasing the power of the eunuchs and political influence.