To provide an efficient simultaneous cleaning means of polluted soil and groundwater.

When cleaning polluted soil and groundwater, soil gas is sucked by a blower from a well; the sucked soil gas-containing air is subjected to liquid separation treatment if necessary, and supplied to a gaseous pollutant detoxifying tank for detoxifying pollutant; polluted groundwater is pumped up from the well at the same time of the above treatment; the pumped-up groundwater is aerated using cleaned air discharged from the pollutant detoxifying tank to vaporize pollutant in groundwater; and the vaporized pollutant is supplied to the pollutant detoxifying tank for detoxification.