The method of isolating organic compound-degradable microorganisms included in this invention is characteristic in that microorganisms in the organic compound contaminated sample, for example an environment sample, are cultured in a carbon-free medium, at the same time, are contacted with organic compounds mainly as the gas phase, and selected by the tolerance to the organic compounds as the index. Also, the method for biodegradation of organic compounds is characteristic in that the microorganism thus isolated, for example, Komagatella brevis, is contacted with contaminated soil or contaminated underground water, and without the addition of additives or inducing substances for organic compounds decomposing enzymes, may effectively biodegrade the organic compounds in the environment.