To easily separate heavy metal contaminants and/or heavy metal-contaminated soil with a constant particle size from clean soil with a simple apparatus without using any special acidic solvent.

This heavy metal-contaminated soil treatment system is provided with wet classification apparatuses like a drum washer 2, a trommel 3, a spiral classifier 4, and a washing screen 7, performing wet classification according to the particle size of contaminated soil S using washing water; a washing water circulation apparatus to repeatingly use the washing water used for the respective wet classification apparatuses by circulating the washing water and supplying it to washing water circulation apparatuses like a buffer tank 11, a repulping tank 12, a filtrate tank 13, a filtrate pump 14, and a water storage tank 15; and a filter press 5 dewatering the washing water from a circulating fluid circulated by the washing water circulation apparatuses, and containing particulate material of a particle size less than 0.2mm and washing water, to obtain the particulate material as contaminant concentrated soil S1.