FINE CELLULOSE FIBER-CONTAINING SUBSTANCE， METHOD FOR MANUFACTURING SAME， AND FINE CELLULOSE FIBER DISPERSION

To provide a fine cellulose fiber-containing substance that has excellent dispersibility in water and can be manufactured easily， a method for manufacturing the fine cellulose fiber-containing substance， and a method for manufacturing a fine cellulose fiber dispersion. A fine cellulose fiber-containing substance contains fine cellulose fibers into which a phosphite containing a cation of an inorganic substance is introduced. The ratio of the cation of the inorganic substance with respect to 1 g of the fine cellulose fibers is 0.14 mmol or more. In manufacturing the fine cellulose fiber-containing substance， a phosphite is introduced into cellulose fibers， and then the cellulose fibers are defibrated to obtain a dispersion containing fine cellulose fibers， during which an alkali metal ion-containing substance is added to the cellulose fibers， and the dispersion is concentrated. In manufacturing a fine cellulose fiber dispersion， the fine cellulose fiber-containing substance is mixed with water.