Acceleration of adjacent segment degeneration(ASD) after spinal fusion has been reported continuously. Change of non-directional factors like von-mises stress, intradiscal pressure, range of motion were checked to solve ASD problem in previously study. But, directionality is important factor. Stress analysis requires consideration of the directionality. In this paper, normal stress and shear stress that are directional factors were checked with two kinds of way. First way is change of stress increment ratio. Second way is correlation analysis between von-mises stress and other factors. First of all, intact lumbar spine model that were based on CT data of a healthy man in his 20s were made by 3-dimensional modeler. Fused model was performed at intervertebral disc between L4 and L5 of intact model. Six motion(flexion, extension, lateral bending, rotating) of the spine were analyzed by finite element method and analyzed data were compared with cadaveric experiment data for validation. As a result of stress incremental ratio, stress level of adjacent segment is higher than others at every motion. Incremental ratio of every factor are similar in each segment. But, correlation coefficients between von-mises stress and z-plane shear stress is the biggest in every motion.