In this study, a peptide exhibiting antioxidant activity was isolated from sandfish (Arctoscopus japonicus) roe hydrolysate (SRH) in order to evaluate their practical uses as materials for manufacturing functional foods. The A. japonicus roe protein was hydrolyzed using Collupulin MG, and isolation of antioxidant peptide was performed using ultrafiltration (UF), prep-HPLC, and RP-HPLC. The SRH with a molecular weight below 3 kDa constituted about 38% of the whole hydrolysate, and the fraction with a molecular weight below 3 kDa showed significantly greater antioxidant activity compared to the original SRH and other fractions. The isolation fold of the antioxidant peptide isolated from SRH throughout the four-step procedure was 7.11-fold, and protein yield was 14.8%. The DPPH radical scavenging activity of isolated antioxidant peptide was above 90% at a concentration of 1.0 mg/mL, which was similar to that of the Trolox at a concentration of 0.1 mg/mL. These results suggested that the antioxidant peptide derived from A. japonicus roe could be a useful additive for producing functional foods and protein supplements. However, it is necessary to perform further study the structural characteristics of this antioxidant peptide isolated from A. japonicus roe.