This study was carried out to investigate the anti-oxidant effect of Wasabia japonica(WJ). The anti-oxidant activities of various extracts from WJ were investigated. The water and ethanol extracts of WJ leaf were found to cause significant free radical scavenging effects on DPPH and nitric oxide(NO). Sprague-Dawley male rats were randomly assigned to one normal diet and three high cholesterol diet groups which contained 1%(w/w) cholesterol. After 4weeks cholesterol diet, the groups of high cholesterol diet were classified to control(normal diet only), WJR5(normal diet and 5% WJ root) and WJL5(normal diet and 5% WJ leaf). Liver xanthine oxidase(XO) activity in the rats of high cholesterol diet was decreased up to the levels of normal diet group according to WJ diet. The results indicated that WJ possesses antioxidant effects through free radical scavenging effects on DPPH, NO and the decreasing of XO activity. In view of these results, WJ is expected to be an effective material for the anti-oxidant.