Provided is a method for remediating arsenic-contaminated soil, including: a collection step of collecting arsenic-contaminated soil; a washing step of adding the collected soil to a washing solution, which is acidic in nature and provides reducing conditions to the soil, so as to remove arsenic from the soil and transfer the removed arsenic to the washing solution; a solid-liquid separation step of separating the soil and the washing solution from each other after the washing step; and a post-treatment step of removing arsenic from the washing solution, which was separated in the solid-liquid separation step, and employing the soil for remediation.