To make relatively easily and efficiently decomposable aromatic ethers represented by dioxin by irradiating the aromatic ethers adsorbed on a solid treated by a heavy metal fixing agent and contg. heavy metals with UV or an electron beam.

The aromatic ethers adsorbed on a solid treated by a heavy metal fixing agent and contg. heavy metals are irradiated with UV or an electron beam to decompose the ethers. In this case, the aromatic ethers mean dioxin, and the solid contg. heavy metals is converted into incineration ash or fly ash. Although the temp. and humidity are not specially limited in the UV and electron beam irradiation when the aromatic ethers adsorbed on the fly ash are treated, the fly ash kept at temp. of ≥40°C, for example, and substantially dried is irradiated as such, or the fly ash can be cooled and humidified, as required, Consequently, the aromatic ethers represented by dioxin are extremely easily decomposed and made nonpoisonous.