Water quality samples were taken for every two hours whenever runoff occurred by rainfall to investigate concentration variations of T-N, T-P and SS during runoff process from a paddy field. The difference between the highest concentration in a runoff event and flow weighted mean concentration for T-N, T-P, SS placed between 3.07∼40.16%, 11.44∼60.80%, and 15.11∼64.5%, respectively. The difference between the lowest concentration in event and event mean concentration for T-N, T-P, SS ranged between -7.24∼-31.84%, -11.59∼-47.86%, and -5.21∼-36.20%, respectively. The relationship between runoff and mass load was derived for each storm event using observed data. The relationship between runoff and mass load showed linear relationship regardless of water quality constituents and rainfall amount. The results suggested that relationship between T-N and T-P loads and runoff should be prepared separately in considering of fertilization effect and seasonal conditions. The relationship between SS and runoff should be made to reflect seasonal conditions and tillage effect.