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 plural fragments among plural fragments that are formed by dividing a sentence by following a preset and prescribed rule and that are included in the first original sentence into other expressions in the first language, by using the processor; identifying one or plural paraphrasing candidate sentences in a same meaning as a meaning of the first original sentence from the plural paraphrasing candidate sentences as one or plural paraphrasing sentences, by using the processor; and creating a translation corpus by generating a new set of sentences by setting the one or plural paraphrasing sentences and the second original sentence as a set of sentences to create a new translation corpus with the new set of sentences or to create a translation corpus by adding the new set of sentences to an existing translation corpus, by using the processor.