In Korea, antibiotic usage has received a lot of attention from the public due to the increasing number of bacteria resistant to the currently used antibiotics. In this study based on FDA regulation and EU draft guideline, the most concerned antibiotics regarding their environmental risk in Korea were assessed and the refined predicted environmental concentration in surface water (PEC(surface water)) was obtained by applying a GIS-based KORea ECOlogical Risk assessment (KOREOCORisk) model. Thirteen antibiotics, which expected introductory concentration (EIC) greater than the trigger value (1.0μg/L), were chosen to assess ecological risk and the PEC/PNEC ratio exceeded 1.0 for amoxicillin, erythromycin and roxithromycin. The results in this study using conservative assumptions did not represent that there is a risk for acute toxic effects in the environment based on today's use of pharmaceuticals in Korea. However, the results do not exclude the potential for chronic environmental effects.