Abstract: A method for purifying a layer of contaminated soil is provided, including the following steps: (a) preparing an injection well for injecting a fluid which has a purification capability utilizing one of physical action, chemical reaction, metabolism of microbes and promotion thereof and highly pressurized washing into the layer and (b) injecting the fluid under a high pressure at which one of the physical action, chemical reaction, metabolism of microbes and promotion thereof and highly pressurized washing can be controlled, through injection nozzles provided on a first wall or a first bottom of the injection well. The method has features that the injected fluid stirs and washes the layer to separate or decompose contaminants and the contaminants are eliminated by collecting the fluid containing an undecomposed portion of the contaminants in the layer through a plurality of collection wells.