According to the present invention, there are provided copper nanoparticles having an average particle diameter of 50 nm or less and having excellent oxidation resistance and dispersion stability. In the collagen peptide-coated copper nanoparticles of the present invention, the copper nanoparticles having an average particle diameter of 50 nm or less are coated with collagen peptides having a weight average molecular weight of 10000 or less.