To establish a method for the conservation treatment of "Hogap"(a leather case to keep a royal seal and its ink pad of the Joseon Dynasty)."Hogap" is referred to as a leather box in which the royal familys treasure and stamp pad were put in the period of the Joseon Dynasty.The royal familys treasure and stamp pad in the period of the Joseon Dynasty was sealed through the three stages.The first stage was for a metallic box including a cylinderical box for treasures and stamp pad; the second stage was for a wooden box including borok and jurok; and the third stage was for a leather box, or "hogap"."Hogap" is comprised of one pair of 2 boxes containing treasures and stamp pad respectively.Through the literature study into "Boinsoeugye", "Gujangdogam", and "Garaedogam", this study investigate the definition of the leather box, production method by period, and materials used for it (leather, backing paper, sorts of adhesives, etc.) and made them into database.As a result of the comparative analysis of the literature and relics regarding hogap, this study confirmed that a lot of parts including leather, color, sewing method, ornamental pattems, and threads, etc.agree with each other.The quilting shown in the relevant literature was found to be the same as the saddle stitch in Europe in terms of its method.We implemented a technology exchange program with the ISCR of Italy(located in Rome) in 2010 for the conservation treatment of leather relics.We applied the result of the program to Hogap, a collection of the National Palace Museum of Korea.The most important conservation treatment of leather relics is to restore their original shape.The cleansing work for color recovering is essential in the treatment, since the quality of the work affects the following works greatly.When the cleansing is completed, the collapsed parts are restored with the indirect injection of moisture.The detached or bloated parts are adhered with wheat-stark glue, by which the conservation treatment is finalized.The focus of this thesis is on the restoration of the original shape of a leather case.