This study analyzes the drawing and fabricating technique of rafter by master carpenter of Korean traditional architecture to reveal the principles of rafter fabrication and to define drawing and fabricating technique. Rafter fabrication of Korean traditional architecture defines the curvilineal line of traditional roofline. Closely examining the principles of fabricating traditional rafter would open possibilities to adapt rafters to various needs and scale without losing the essential quality. Simultaneously the analysis and recording of rafter fabrication documented in this study will contribute to the preservation and propagation of tradition that could have been only relied on skills of master carpenters. Rafter of Korean traditional architecture is made of wood in various size and different curvature, which necessitates drawing and fabrication method called "Yeon Mok Jya Pan(연목좌판, 椽木坐板)". Therefore apprehending the workings of this method is crucial in understanding the specification and fabrication technique method. Various conditions and analysis results were found through this study.