The Park Youngjin family, a Gaeseong merchant of Korea, revealed recently old accounting books(Park’s book) which had been preserved by its ancestors. This record spans 1887 to 1912. Jun et al(2013) and Huh(2015, 2016) found that the Park’s book had been recorded based on a verifiable double-entry bookkeeping that is indigenous to Korea. This result settled the controversy of whether or not the traditional Korean accounting of the Sagae Songdo Chibubeob is double- entry bookkeeping. The Korean government designated the Park’s book as a Listed National Cultural Heritage No. 587. The book shows that the management of ginseng field was the major business of the Park’s family from 1897 to 1904. Ginseng fields were managed by Dojung which is similar to partnership. During this period thirty four dojungs were established and controlled as subsidiaries. The ratios of ginseng field related assets to total assets were ranged between 45.6 percent in 1901 and 80.2 percent in 1899. This study examines details of ginseng field accounting of the Park’s book for further understanding of Sagae Songdo Chibubeob. The result shows that ginseng field related transactions were journalized and posted to general ledger and the subsidiary ledger, Gagin Hoegyecheg, by the name of individual dojung, accounted based on double-entry bookkeeping principles. Investment in and revenue from ginseng field were journalized on debit and credit, respectively. However, revenue from dojung was not recognized until the year just before its closing individual dojung account. Instead, the balance of debit after subtraction of credit amount was carried forward to the next year as unrecovered investment. This balance was reported on balance sheet as an asset at the end of accounting year. Net income was computed by subtracting unrecovered investment from revenue generated in closing year. Dojung was dissolved after distribution of its net income to its members. The accounting record in dojung of ginseng field contains modern thoughts and techniques of management. Dojung accounting computed and added cost of capital to its investment and revenue. This indicates that the net income of dojung corresponds to residual income in modern management accounting. The Park Youngjin family's accounting book is the first and only record which recognizes explicitly cost of capital in accounting book. Market price was applied to internal transfer pricing when nursery ginseng was transplanted. Gaeseong merchant was far ahead of the West considering that optimal transfer pricing was begun to be discussed in 1950's. The fact that net income of dojung was distributed equally to its members is the result that capital, professional knowledge to grow ginseng, and management know-how which were contributed to dojung were valued equally. Together with the low level of cost of capital applied, equal distribution of income implies that Gaeseong merchant practiced management based on mutual dependence and survival. This is unusual in current practice in which capital dominates. There were efforts to avoid various risk inherent to growing ginseng such as forming dojung and timely response to market condition. These modern thoughts and techniques of management are evidence reflecting Gaeseong merchant's rational economic activities in the turn of the 20th century Joseon dynasty.