To provide a method which can purify oil-contaminated soil using microorganisms without incurring high cost in a short time with high efficiency, and to provide a method which efficiently purifies oil-contaminated soil by combining a plurality of techniques in an oil-contaminated soil purification process using selected excellent bacteria.

A nutritional supplement 4, 11 and a bacterial material 5, 12 are added to oil-contaminated soil 1, 10, and the oil-contaminated soil is purified by microorganisms. A previously prepared bacterial culture base may be added to the oil-contaminated soil. The addition of an oil atomizing agent, an oil adsorbing agent, an oil decomposition enzyme, a gelling agent, or the like, to the soil can further improve the purification level.