The purpose of this paper is to examine the strengthening of eldest son preferences in inheritance in modern Korea by focusing on the case of land inheritance. It is common knowledge that the eldest son-based inheritance practice in Korea originated in the late Joseon dynasty and was linked to the domination of Confucian ideology. However, considering the land inheritance cases during the modern period, it seems that the eldest son-referential inheritance practice actually strengthened in the 20th century. This paper investigates continuity and change in land inheritance practice from the colonial period to the modern period. We examine the land inheritance patterns of the Andong Kwon and Suncheon Park clans who resided in Shindeung-myun, South Gyeongsang Province. We make use of land registers, household removal records, and genealogies. This provides annual records of land ownership as well as information about family relationships among the owners. Through this analysis, we will examine how the Korean inheritance practices that favored eldest sons evolved in the first half of the 20th century.