1. A method of constructing translation knowledge, comprising: receiving a source-language sentence and a target-language sentence corresponding to translation of the source-language sentence; converting the source-language sentence and the target-language sentence into a form that is expressed with syntactic information; performing word alignment and syntactic alignment of the converted source-language sentence and the converted target-language sentence; and extracting translation knowledge on a subcategory of a bilingual inflected-word from results of the word alignment and the syntactic alignment by using information on dependency relationship.