Method for producing oxidation process and cellulose nanofiber cellulose

To provide a method for efficiently introduce a carboxyl group to promote the oxidation of primary hydroxyl groups of the cellulosic material. Further, fluidity, to provide a method for efficiently producing the transparency and thermal stability superior cellulose nanofibers dispersion with low energy. (1) N-oxyl compound, and (2) bromide, in the presence of iodide or compound selected from the group consisting of mixtures of cellulosic material by a hypohalite under conditions pH8~11 oxidized, by introducing 1.0 mmol / g or more carboxyl groups with respect to the absolute dry weight of the cellulosic material, and then further oxidized by halite under the conditions of pH 4-6. Resulting oxidized cellulosic material to give a cellulose nanofiber dispersion by defibration and dispersion treatment.