1. An apparatus for improving a bilingual corpus including a plurality of sentence pairs of a first language and a second language and word alignment information of each of the sentence pairs, the apparatus comprising: an extracting unit configured to extract a split candidate from word alignment information of a given sentence pair; a calculating unit configured to calculate split confidence of said split candidate; a comparing unit configured to compare said split confidence and a pre-set threshold; and a splitting unit configured to split said given sentence pair at said split candidate in a case that said split confidence is larger than said pre-set threshold.