The purpose of this study was to consider the changes of rafter fixation methods of Jeongjagak in the later Joseon period. For this purpose, forty two official reports of royal tombs in Joseon dynasty were analized for the measurement methods of rafter amount, the changes of rafter fixation, the installation methods of rafter nails and its connecting niddles. Jeongjagak has been known for government construction in Joseon dynasty which has enhanced construction and bearing capabilities of rafter work by using rafter nails to fix the rafters. As a result, it was induced to increase the comparison rate of rafter nail and to widen the fixed part.