The first purpose of this study is to find out the factors that gave jangsagak or sagak(pavilion keeping national annals) of J eonjoksan sago(national archives storehouse) in Ganghwa island single-story elevation which was notably different from the other sagaks of local sagos that had double-story structure. The second purpose is to estimate the column arrangement and interior of jangsagak, which is indistinct for lack of historical materials. There were two factors that were possible to affect the single-story elevation of jangsagak; first, the influence of the building of Manisan sago, the former sago of Ganghwa island, which had diverted a single-story J aegung(purification house) to a storehouse; second, the need to consider the convenience of searching and carrying out the historical materials to perform the roll of substancial naesago(central storehouse of national archives). Unlike the contemporary rebuilt jangsagak, the side of original jangsagak is estimated to be composed of two or three kans at regular intervals of 2.7m. And, it is highly probable that original jangsagak had dense interior column arrangement. In both ends of jangsagak building, there could be lofts to adopt the advantage of double-story sagaks and to get the additional working area for the reference and taking out the historical materials.