The present invention relates to a method of cleaning up a soil contaminated with organic matter such as oil without the need of pH adjustment or the emission of bad odors, said method comprising adding organic materials such as compost that have been completely fermented and matured to a soil contaminated with organic matter so that the indigenous microorganisms are activated to degrade and remove contaminants in the soil. In addition to adjusting pH of the soil to about neutral with organic materials, the method of the present invention promotes the degradation and removal of the contaminants in the soil through the microorganisms that were introduced by the organic materials.