PURPOSE : A real estate operating system and a method thereof are provided to supply one part of loan to creditor after trading one part among share of real estate as an investment, thereby one part of debt can be repaid. CONSTITUTION : A creditor holds constant part among share of an apartment. By selling 40% of share, investment(45) is provided to an external investor(50). For suggesting fixed rate or floating rate, the external investor separately manages one part among sale price of investment as interest and operation expenses(52). Through share of creditor or assurance of the creditor through security, a principal of investment of investor is guaranteed.