Résumé dans la langue de publication, traduction non disponible The aim of the present invention is to propose a simple procedure which make it possible to seal off surely a various kind of hazardous metals contained in a final waste generated from an incineration of wastes and to stabilize hazardous metals etc. not to leach out again. In a waste gas disposal machine attached to a waste incineration equipment, an acidic gas contained in waste gas generated at time of a waste incineration such as hydrogen chloride or SOx can be effectively captured by blowing into a waste gas generated at time of a waste incineration a high reactive neutralizing agent such as either water glass, calcium hydroxide or powdery calcium silicate hydrate of above 20 m**2 /g or more preferably above 30m**2 /g specific surface area according to the present invention. And further, according to the present invention, it is possible to stabilize hazardous metals contained in an ash by either blowing into this waste gas a stabilizing agent or by adding a stabilizing agent for hazardous metals to an ash collected from waste gas and kneading the mixture. The present invention is effective not only for disposal of waste gas from an industrial or a municipal waste incineration furnace but also for stabilizing disposal for hazardous metals contained in an ash from Eash or a bag ash generated from this waste gas, and an ash collected from waste gas disposed by blowing a neutralizing agent of an acidic gas is easy to be disposed after being captured.