The objective of this study was to evaluate the antimicrobial and antioxidative effects of the onion peels extract prepared via the subcritical water extraction (SWE) method. First, the number of cells treated with the extract was reduced by 0.7-1.1 log CFU/mL compared with the control. The SWE extract showed 76.08% scavenging activity and it was more effective than butylated hydroxytoluene (BHT) at 61.3 ppm in lipid peroxidation inhibitory effects. In addition, the antioxidative effect of SWE extract measured via the ferric thiocyanate (FTC) method was 2-fold that of BHT. The results of this study suggest that the onion peels extract prepared via the SWE method may have potential alternative antimicrobial and antioxidative effects as functional substances.