Abstract: A contaminated soil remediation method activates a microorganism in soil contaminated with a toxic chemical substance. The contaminant is decomposed by a biodegradation reaction of the microorganism. The method involves forming a boring hole reaching into contaminated soil. A rod whose end is provided with a jet device is inserted into the boring hole. The contaminated soil is cut in a manner forming a flat-plate area in which the soil is intermittently cut by a microorganism activator, and the soil and the microorganism activator are mixed, by jetting water and/or the microorganism activator from the jet device.