A water-based composition containing: (A) fine cellulose fibers having a number-average fiber diameter of 0.5 nm or more and 200 nm or less, and having a carboxy group content of 0.1 mmol/g or more, wherein the carboxy group forms a salt with an alkali metal and (B) an additive containing one or more compounds having carbon atoms and nitrogen atom or atoms, wherein a ratio thereof per molecule of the compound (number of carbon atoms/number of nitrogen atoms) is 3 or more and 45 or less, wherein the content of the component (A) is 0.2% by mass or more and 10% by mass or less, and wherein the content of the component (B) is 3 parts by mass or more and 150 parts by mass or less, based on 100 parts by mass of the component (A), and wherein the water-based composition has a viscosity at 80°C at a rotational speed of 30 rpm of 80 mPa•s or more. Since the fine cellulose fibers or a salt composite thereof of the present invention retains a high viscosity even under high temperatures, the fine cellulose fibers or a salt composite thereof can be suitably used in various industrial applications represented by thickening agents during gas and oil drilling, cosmetic applications, and other applications requiring manufactured article stability at high temperatures.
