An object of the present invention is to provide a soil improvement method capable of improving soil by a simple operation. The soil improvement method of the present invention is a soil improvement method in which nano-bubble water is applied to the soil.本發明的課題在於提供一種可藉由簡便的操作而改良土壤的土壤的改良方法。本發明的土壤的改良方法為將奈米氣泡水施用於土壤的土壤的改良方法。