1. A method for establishing paraphrasing data for a machine translation system comprising: selecting a paraphrasing target sentence through application of an object language model to a translated sentence that is obtained by machine-translating a source language sentence; extracting the paraphrasing candidates that can be paraphrased with the paraphrasing target sentence from a source language corpus DB; performing machine translation with respect to the paraphrasing candidates; selecting a final paraphrasing candidate by applying the object language model to the result of the machine translation with respect to the paraphrasing candidates; and confirming the paraphrasing target sentence and the final paraphrasing candidate as paraphrasing lexical patterns using a bilingual corpus and storing the paraphrasing lexical patterns in a paraphrasing DB.