Chlorine dioxide gas is immediately generated at a stable concentration from a liquid composition. The composition is obtained by mixing an aqueous chlorite solution, an activator that immediately adjusts the pH of the aqueous chlorite solution, an activation inhibitor that slowly mitigates an action of the activator, and a metal iodide such that the metal iodide is contained in a proportion of 0.4% by mass or less and the activation inhibitor is contained in a proportion of 1% by mass or less with respect to 1 L of 1% by mass aqueous chlorite solution.
