The goal of this study is to analyze the effects of geometries of mortise and tenon on moment carrying capacity of the “sagae” connection. Effects of different tenon widths, mortise depths of connection from the top and bottom beams on stress distribution were investigated using the finite element method (FEM). Critical normal and shear stresses occurred at the reentrant corner from the mortise of the bottom beam. The maximum moment carrying capacity of the sagae connection from the FEM was validated from the results of experimental test. Maximizing moment carrying capacity of the sagae connection was found when the tenon width and mortise depth from the two beams were 40 mm and 60 mm, respectively.