1. A translation machine for translating an original sentence of a source language into a translated sentence of a target language, comprising: storing means for storing a syntax priority rule of said source language, including partial structures of said source language, numerical values each indicating a priority of one of said partial structures, and incidental conditions of each of said partial structures; a translation module for translating said original sentence into a plurality of sentences of said target language having different syntactic structures, respectively, said translation module including structure deriving means for deriving a plurality of syntactic structures of said original sentence based on said partial structures and said incidental condition, and priority deriving means for deriving priority magnitudes of said plurality of syntactic structures respectively, based on said numerical values; and control means for performing a control to output one of said plurality of sentences of said target language as said translated sentence, in accordance with said priority magnitudes.