To provide a compact washing apparatus of contaminated soil providing reusable soil by continuously washing and sorting contaminated soil contaminated with heavy metals like arsenic, and separating contaminants.

A drum washer 3 is disposed between trommels 2, 4 for rough washing and finish washing; partition plates 7, 7a are provided at boundary parts 5, 6 thereof along inner peripheral faces to integrate them; washing water supply pipes 12, 13 for rough washing and finish washing are provided inside to form the washing apparatus of contaminated soil. The apparatus is installed on a washing line, being slightly tilted from the upstream trommel 2 toward the downstream trommel 4 by 3-10°. This integration makes the apparatus compact, saves an installation space, greatly reduces facility cost, suppresses flowing out of washing drain toward the downstream side, and efficiently regenerates the contaminated soil.