The purpose of the study is to analyze the 'A Judge - Nepotism', So called Song Khan Sang Pi Jae(訟官相避制), in terms of holding in check political familism or bureaucratic collusion. Based on the Materials, the writer also scrutinized such laws and ordinances of Chosen dynasty as Kyung Guk Dae Jeon(經國大典), and Kyul Song U Chui Bo(決訟類聚補), and Wang Jo - Sil Rok(王朝實錄), etc. Once examining the documents above mentioned, the writer also analyzed the contemporary genealogical records of the influential or prominent political family for the purpose of finding pratical procedings or results. Conclusively the thesis is mainly concentrated on the study of Sang Pi Jae (相避制) during the period of a early Chosen dynasty. However one may easily find its significance of the constitutional transition and shift in the early dynasty, as Considered the political effects on the late Chosen dynasty.