A method for handling a sample of a biochemical substance with a biochemical tool is provided. The method comprises a step of bringing the sample of the biochemical substance into contact with the biochemical tool. The sample of a biochemical substance includes nucleic acids. The biochemical tool comprises a part configured to contact the sample of the biochemical substance, the part being made of a resin composition containing at least one cycloolefin polymer selected from the group consisting of a copolymer of a cycloolefin and a chain olefin, a ring-opened polymer of a cycloolefin, and a hydrogenated product of a ring-opened polymer of a cycloolefin, and an antioxidant, the resin composition comprising 0.01 parts by mass or more and 0.7 parts by mass or less of the antioxidant relative to 100 parts by mass of the cycloolefin polymer.