1. A translation corpus creation method comprising: receiving a first original sentence in a first language and a second original sentence that is the first original sentence which is translated into a second language different from the first language, by using a processor; generating plural paraphrasing candidate sentences for the first original sentence by paraphrasing one or more fragments of plural fragments that are obtained by dividing the first original sentence using a preset and prescribed rule, into other expressions in the first language, by using the processor; identifying one or more paraphrasing candidate sentences having a same meaning as a meaning of the first original sentence, of the plural paraphrasing candidate sentences, as one or more paraphrasing sentences, by using the processor; and creating a translation corpus by generating a new set of sentences by associating the one or more paraphrasing sentences with the second original sentence, and by creating a new translation corpus with the new set of sentences or by adding the new set of sentences to an existing translation corpus, by using the processor.