To provide a technique for economically and efficiently purifying the soil contaminated by an organochlorine compd. such as dioxins.

The soil contaminated by an organochlorine compd. is purified by this method, and the method is provided with a mixing stage for admixing powdery aluminum with the contaminated soil, a heating stage for heating the obtained mixture to a temp. at which a thermit reaction takes place between the aluminum and a component of the contaminated soil and a sintering stage for thermally decomposing the organochlorine compd. in the mixture by the thermit reaction caused by the heating stage and sintering the mixture.