To provide a method of treating polluted soil and device therefor in which equipment is miniaturized and continuous operation is made possible and by which dioxins can be effectively removed.

In a method of treating polluted soil for obtaining treated soil 13 from which dioxins in polluted soil 9 have been removed by thermal treatment of the polluted soil 9, the polluted soil 9 is heated to 400 to 600°C to evaporate dioxins or partially decompose them and gas containing the evaporated dioxins is sent to a dioxin decomposition furnace 17 to heat the gas to thermally decompose the dioxins. Since the polluted soil is heated to 400 to 600°C, the dioxins are evaporated or partially decomposed, the treated soil 13 from which the dioxins have been removed is obtained and a furnace 4 for heating the polluted soil 9 is miniaturized. Even if sodium chloride is contained in the polluted soil 9, gaseous chlorine is not generated and the corrosion or the like of equipment 30 is sufficiently prevented.