We conducted two three-dimensional numerical models to investigate the effects of the surrounding surface surcharge on the deformation of the retaining structure. The results obtained by the finite element model are in good agreement with the field measurements. The deflection of the diaphragm wall increased by 2-3 times owing to the surrounding surface surcharge, which implies that the surrounding surface surcharge magnifies the excavation-space effect. The maximum wall deflections were approximately 0.03-0.05 H (H is the excavation depth) in the case without surface surcharge. However, the maximum wall deflections increased up to 0.05-0.19 H when surrounding surface surcharges were applied on the surface ground around excavation. The surrounding surface surcharge leads to the increase of the maximum wall deflection.