To solve the problems wherein the rapid cleaning and finishing are difficult by the occurrence of secondary pollution because of production and accumulation of byproducts accompanied with the dechlorination of an organic chlorine compound in the conventional method for cleaning underground water or soil polluted by organic chlorine compounds by using microorganisms.

The cleaning of tetrachloroethylene, trichloroethylene, dichloroethylene, tetrachloromethane, trichloromethane and dichloromethane is rapidly carried out without forming the byproducts by using the new Clostridium sp. KD13 (accession number: FERM P-21115) or the cleaning preparation containing the Clostridium sp. KD13.