A fixing liquid for properly and economically suppressing or preventing dispersion of dust (asbestos dust) generated through weathering or demolition of a sprayed-on material containing asbestos is prepared by homogeneously incorporating a surfactant and a thickener (e.g., CMC) into a solution of a polysaccharide (e.g., gum arabic). When an appropriate amount of the fixing liquid is sprayed onto a sprayed-on material containing asbestos, dust due to weathering of the sprayed-on material is wetted and retained, and dispersion of dust generated during demolition of the material is suppressed or prevented. Even after drying of the fixing liquid, the viscosity of the liquid is restored by re-wetting with water, and dispersion of dust generated during demolition of the thus-treated material is suppressed or prevented. Since the thickener has an increased volume in the presence of water, the thus-treated material is readily removed.