The invention relates to an indirect thermal desorption device which comprises a feeding part, an auxiliary part, a heating part, a dedusting part, a washing and cooling part, a waste liquid purifying-recycling part, a waste gas adsorbing and filtering part, a discharging part and a monitoring part, wherein the feeding part and the auxiliary part are connected with the heating part, the discharging part comprises a gas discharging device and a soil discharging device, the washing and cooling part is a washing and cooling tower, the waste liquid purifying-recycling part is connected with the washing and cooling tower, the heating part is orderly connected with the dedusting part, the washing and cooling tower and the waste gas adsorbing and filtering part, the heating part, the dedusting part, the washing and cooling tower and the waste gas adsorbing and filtering part are also respectively connected with the monitoring part, and the waste gas adsorbing and filtering part is connected with an air introducing device in the auxiliary part. The invention has the advantages of large treatment capacity, low treatment cost, soil physicochemical property maintenance and the like, can effectively separate organic matters from contaminated soil and treat the organic matters, and also can complete the processes of waste gas washing, waster gas adsorption and the like so as to reduce the energy consumption of the overall system.