Provided is a method of disinfecting or inactivating a germ or virus floating in a space, the method comprising the steps of: preparing a humidifier filled with an aqueous solution containing hypochlorous acid as a main component; and operating the humidifier to spray the aqueous solution containing hypochlorous acid as a main component into the space; wherein the spraying is performed while humidifying the space, and wherein 40 mol % or more of chlorine in the aqueous solution is chlorine that makes up hypochlorous acid.