In order to examine oxidative stress of reactive oxygen species and the antioxidant effect of Citri Reticulatae Pericarpium (CRP) extract, human skin melanoma cells were treated with various concentrations of hydrogen peroxide ($H_2O_2$). Antioxidant effect of CRP extract on $H_2O_2$-induced cytotoxicity, cell viability, DPPH-radical scavenging activity and superoxide dismutase (SOD)-like activity. In this study, $H_2O_2$ decreased cell viability of cultured human skin melanoma cells in dose- and time-dependent manners, and then, midcytotoxicity value (MCV) was determined at $60;{mu}M$ after human skin melanoma cells were cultured for 5 hours in the media containing $20{sim}60;{mu}M$ of $H_2O_2$, respectively. The $H_2O_2$ was on cultured human skin melanoma cells because MCV of $H_2O_2$ was lower than $100;{mu}M$. In the antioxidant effect of CRP extract, CRP extract increased cell viability DPPH-radical scavenging activity and SOD-like activity. From these results, it is suggested that $H_2O_2$ was very toxic on cultured human skin melanoma cells. And also, CRP extract has the antioxidant effect on $H_2O_2$-induced cytotoxicity.