We investigated 52 livestock farming complexes in Gyeong-Gi and Incheon provinces based on low, medium, and high livestock density and groundwater quality. The objective of this study was to evaluate a relationship between nitrate N concentration in groundwater and animal factors, such as livestock density and animal species. 2,200 groundwater samples for 3 years from 2012 to 2014 at Gyeong-Gi and Incheon provinces were collected and analyzed for pH, EC, DO, ORP, temperature, major anions and cations, such as $NO_3-N$, ${HCO_3}^-$, ${PO_4}^-$, ${SO_4}^{2-}$, $Cl^-$, $NH_4-N$, $K^+$, $Na^+$, $Ca^{2+}$, $Mg^{2+}$, T-N, and TOC. Average concentration of total N for generated load density was $23,973g\;day^{-1}\;km^{-2}$ for cattle, $51,551g\;day^{-1}\;km^{-2}$ for pig, and $52,100g\;day^{-1}\;km^{-2}$ for poultry. For animal feeding species, average ratio for generated load over discharge load was 16.1% for cattle, 7.8% for pig, and 7.1% for poultry. Therefore, cattle feeding region is highly vulnerable for water pollution compared to pig and poultry feeding areas. The concentrations of chloride, nitrate, and total N in the groundwater samples were higher at high animal farming regions than other regions. The average concentration of nitrate, and chloride in groundwater samples was $5.0mg\;L^{-1}$, $16.6mg\;L^{-1}$ for low livestock density, $6.9mg\;L^{-1}$, $17.7mg\;L^{-1}$ for medium livestock density and $7.6mg\;L^{-1}$, $22.7mg\;L^{-1}$ for high livestock density and total nitrogen (T-N) was $7.7mg\;L^{-1}$ for low livestock density, $9.4mg\;L^{-1}$ for medium livestock density, $10.7mg\;L^{-1}$ for high livestock density. In conclusion, based on this research, for managing groundwater quality near livestock farming regions, $Ca-(Cl+NO_3)$ group from the Piper diagram is more efficient than using 19 factors for water quality standard.