To provide a method capable of attaining the treatment and the carbonation intended at that time with a little cost from the structural and method ological point of view and capable of binding heavy metal to residue or cinder as good as possible in a method for treating the cinder generated from a device for treating combustion residue, especially from a waste incinerator.

A hydrogencarbonate soln. is used preferably as a carrier medium in order to carbonize the combustion residue generated at an incinerating stage, especially for treating the cinder at the waste incinerator. The hydrogencarbonate soln. produced in a reaction vessel 12 is supplied to the cinder from upward at a filling passage 5 by using cinder water and the carbon dioxide from waste gas.