PURPOSE: To secure the homogeneousness and the uniformity of a caked body, to eliminate harmful vacant spaces and to improve the strength by dividing incineration ash to lumpy materials and powdery materials and forming powdery materials into pellets and putting both of them in one or independent caking vessels to cake them.

CONSTITUTION: Incineration ash transported by an ash transporting conveyor 4 is applied to a crusher and classifier 5, and relatively soft lumpy ash is made into powdery materials by a tapping ball 6. Powdery materials are sieved by a sieve 7 and are formed into pellets by a granulator 8 and are recovered in a drum can 9. Lumpy materials consisting of metallic materials and lump of ash having a prescribed hardness or more are discharged from the upper part of the sieve 7 and are recovered in the drum can 9. A caking agent and water are kneaded by a means 12 and are charged into the drum can 9 by a means 13 to cake these materials. Since powdery materials are formed into pellets, powdery materials do not exist in gaps among lumpy materials and pellets stored in the drum can 9. Consequently, the chargeability of the caking agent is not hindered and lumpy materials have a certain or higher strength, and therefore, a caked body is obtained which has no vacant spaces and has stable physical properties and strength.