This study investigates the effect of tri-directional loading on the in-plane shear ultimate capacity of shear walls through loading tests and finite element analysis. The evaluation method considering tri-directional loading conditions for shear capacity of walls is modified and is applied to various sections including rectangular sections, and a low standard deviation of 0.04 or less is achieved for each test specimen shape, enabling high-precision evaluation. Results show an average safety factor of 1.28 using the Hirosawa mean equation with an out-of-plane deformation angle of 1.5%, based on past experimental databases.