Abstract: Provided is a plasma oxidation-reduction method with which it is possible to control the structure of amino acids and proteins with high and stable reproducibility, by using plasma in order to control the amino acids and proteins that make up a living body, particularly by using plasma in order to oxidize or reduce amino acids and proteins. Also provided are a method for promoting plant/animal growth using the plasma oxidation-reduction method, and a plasma-generating device for use in the method for promoting plant/animal growth. Amino acids or proteins are oxidized or reduced in the plasma oxidation-reduction method by using an active oxygen species or active hydrogen in the plasma. Preferably, the active oxygen species comprises any one of singlet oxygen atoms, excited oxygen molecules, or hydroxyl radicals, and the active hydrogen comprises excited hydrogen atoms.