This study examined the effects of socket flexion angle in trans-tibial prosthesis on stump/socket interface pressure. Ten trans-tibial amputees voluntarily participated in this study. F-socket system was used to measure static and dynamic pressure in stump/socket interface. The pressure was measured at anterior area (proximal, middle, and distal) and posterior area (proximal, middle, and distal) in different socket flexion angles ($5^{circ}$, $0^{circ}$, and $10^{circ}$). Paired t-test was used to compare pressure differences in conventional socket flexion angle of $5^{circ}$ with pressures in socket flexion angles of $0^{circ}$ and $10^{circ}$ (${alpha}$=.05). Mean pressure during standing in socket flexion angle of $10^{circ}$ decreased significantly in anterior middle area (19.7%), posterior proximal area (10.4%), and posterior distal area (16.3%) compared with socket flexion angle of $5^{circ}$. Mean pressure during stance phase in socket flexion angle of $0^{circ}$ increased significantly in anterior proximal area (19.3%) and decreased significantly in anterior distal area (19.7%) compared with socket flexion angle of $5^{circ}$. Mean pressure during stance phase in socket flexion angle of $10^{circ}$ decreased significantly in anterior proximal area (19.6%) and increased significantly in anterior distal area (8.2%) compared with socket flexion angle of $5^{circ}$. Peak pressure during gait in socket flexion angle of $0^{circ}$ increased significantly in anterior proximal area (23.0%) compared with socket flexion angle of $5^{circ}$ and peak pressure during gait in socket flexion angle of $10^{circ}$ decreased significantly in anterior proximal area (22.7%) compared with socket flexion angle of $5^{circ}$. Mean pressure over 80% of peak pressure ($MP_{80+}$) during gait in socket flexion angle of $0^{circ}$ increased significantly in anterior proximal area (23.9%) and decreased significantly in anterior distal area (22.5%) compared with socket flexion angle of $5^{circ}$. $MP_{80+}$ during gait in socket flexion angle of $10^{circ}$ decreased significantly in anterior distal area (34.1%) compared with socket flexion angle of $5^{circ}$. Asymmetrical pressure change patterns in socket flexion angle of $0^{circ}$ and $10^{circ}$ were revealed in anterior proximal and distal region compared with socket flexion angle of $5^{circ}$. To provide comfortable and safe socket for trans-tibial amputee, socket flexion angle must be considered.