A method of decreasing nitrate nitrogen and volatile organic compounds in soil and groundwater by burying a fatty acid having 10 or more carbon atoms, an alcohol having 12 or more carbon atoms, an ester of a linear saturated fatty acid having 14 or more carbon atoms and a monohydric alcohol, an ester of a linear saturated fatty acid having 14 or more carbon atoms and a polyhydric alcohol, an ester of a fatty acid having 16 or more carbon atoms and glycerine, and the like in soil containing nitrate nitrogen and volatile organic compounds or by contacting groundwater with same. This method allows for on site treatment, high biological denitrification and a decrease in volatile organic compounds secondary pollution by the release of organic matter and nitrogen into the environment.