The present study was to investigate the in vitro antioxidant potential of hot water extract and its fractions from dichloromethane ($CH_2Cl_2$), ethyl acetate (EtOAc), n-butanol (n-BuOH), and water ($H_2O$) of castor-aralia (Kalopanax pictus) leaves using different antioxidant tests. Among these crude extract and fractions, EtOAc fraction exhibited higher antioxidant potency than others in 1,1-diphenyl-2-pricylhydrazyl (DPPH) free radical scavenging, reducing power assay, and reactive oxygen species (ROS) scavenging activity. However, $CH_2Cl_2$ fraction showed higher hydroxyl radical scavenging and DNA damage protective activity. This work demonstrates the potential of castor-aralia leaves as antioxidant functional food ingredients.