To provide a safe and inexpensive fluidizing treatment working method good in fluidity and workability affording high-strength soil.

The fluidizing treatment working method comprises the following practice: quicklime is added to raw material soil followed by mixing and disaggregation. The resultant modified soil thus lime-treated is admixed with slag, calcium sulfate and water to prepare fluidizing-treated soil. A predetermined filling structure is worked using a placing apparatus.