a process and an apparatus are provided for conducting decontaminating efficiently polluted soil in plural areas . the process comprises steps of decomposing a decomposition - object collected from a first area , interrupting the decomposing step , transporting the decomposition - object remaining to be decomposed after the interrupting step to a second area , and decomposing the transported decomposition - object together with a decomposition - object collected from the second area , wherein the first decomposition - object collected from the first area and the second decomposition - object collected from the second area are the same substance . the apparatus for decomposing a decomposition - object comprises a receiving means for receiving an undecomposed decomposition - object transported from a first area to a second area , and a decomposing means for decomposing , in the second area , the transported decomposition - object together with a decomposition - object collected from the second area , wherein the transported decomposition - object and the decomposition - object collected from the second area are the same substance .