The present invention provides a functional peptide having excellent antioxidant activity, the peptide having excellent biocompatibility and significantly better antioxidant activity than conventional GSHs in order to overcome the limitation of the weak antioxidant activity of existing peptides. The peptide of the present invention can promote antioxidant activity or effectively repair biological tissue or cell damage caused by reactive oxygen species generated due to oxidative stress. Therefore, the peptide having such antioxidant activity effectively acts on cell damage caused by oxidative stress, and can thus be used to prevent and repair cell damage.