To improve final translation quality by reducing the level of ambiguity in selection of a best translation candidate from translation candidates obtained by a plurality of mechanical translation parts.

The mechanical translation system 130 comprises mechanical translation devices 30A and 30B each of which outputs an English translation candidate to a Chinese common input sentence; and a selector 182 which receives the translation candidates, calculates, based on a determination reference using a language model group 150A and a translation model group 152 and on a determination reference using a language model group 150B and a translation model group 152B, which are obtained from parallel text corpuses 142 and 144 differed in property, both scores of each translation candidate, and selects and outputs, based on the scores, either one of the translation candidates outputted by the mechanical translation devices 30A and 30B as a translation output 160.

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