For introducing the groundwater quality assessment using background concentration of groundwater, severalmethods had been studied to estimate the background concentration of groundwater and to suggest the background concentrationof study area. Some methods such as Box whisker plot, Percentile and Cumulative probability distribution had been adoptedto estimate background concentration, and it was evaluated that the Cumulative probability distribution method presents morereasonable background concentration because it can consider the data distribution. So we estimated the background concentrationof study area using cumulative probability distribution method. We suggested the background concentration for eachhydrogeology respectively in case hydrogeological water quality similarity is very low.