Disclosed herein is a method for treatment of arsenic-contaminated soil, said method being capable of insolubilizing arsenic compounds (in organic form or tri- or pentavalent inorganic form), thereby reducing their leaching level below the environmental standard value for soil. The method consists of heating arsenic-contaminated soil at 200 to 700.degree. C. and mixing the heated soil with a calcium compound and water. The method also consists of mixing arsenic-contaminated soil with a calcium compound, heating the mixed soil at 200 to 700.degree. C., and mixing the heated soil with water.