The present invention provides a carrier for immobilizing a bio-derived polymer, and especially, the present invention provides a carrier of diamond fine particle for immobilizing a DNA, RNA, protein and peptide, as well as a DNA chip substrate, a carrier for trapping virus and a vaccine. The carrier is prepared by the steps comprising: preparing an initial mixture including a diamond and a non-diamond by means of explosion of a detonating agent; subjecting the initial mixture to an oxidation treatment to obtain a suspension solution including the diamond; and separating a phase including the diamond. According to the present invention, after the oxidation treatment, a basic material having per se volatility or to generate a decomposed material having volatility is added, to neutralize with nitric acid, and thereby obtained diamond fine particle has a functional group on the surface thereof.