A language model generating device comprising: a paraphrase generating unit adapted to generate, by using morphemes of a phrase included in learning example sentences that include a plurality of sentences and using synonyms for original expressions of the morphemes, a plurality of paraphrases that include a combination of an original expression of a morpheme and a synonym for an original expression of a morpheme and a combination of synonyms for original expressions of morphemes; a paraphrase sentence extracting unit adapted to extract and output, from a corpus that includes a plurality of sentences, a paraphrase sentence that includes any of the plurality of paraphrases; an original sentence extracting unit adapted to extract and output, from the learning example sentences, an original sentence that includes the phrase; an n-gram generating unit adapted to generate n-grams from the original sentence; a likelihood calculating unit adapted to calculate a likelihood that indicates whether the paraphrase sentence input from the paraphrase sentence extracting unit is similar in context to the original sentence input from the original sentence extracting unit based on the n-grams input from the n-gram generating unit and the paraphrase sentence input from the paraphrase sentence extracting unit; a paraphrase extracting unit adapted to extract a paraphrase included in a paraphrase sentence whose likelihood has a value that indicates a higher degree of similarity in context to the original sentence than a threshold value; and a language model generating unit adapted to generate a language model for automatic speech recognition that is based on an n-gram model from the paraphrase extracted by the paraphrase extracting unit and the learning example sentences. a paraphrase generating unit adapted to generate, by using morphemes of a phrase included in learning example sentences that include a plurality of sentences and using synonyms for original expressions of the morphemes, a plurality of paraphrases that include a combination of an original expression of a morpheme and a synonym for an original expression of a morpheme and a combination of synonyms for original expressions of morphemes; a paraphrase sentence extracting unit adapted to extract and output, from a corpus that includes a plurality of sentences, a paraphrase sentence that includes any of the plurality of paraphrases; an original sentence extracting unit adapted to extract and output, from the learning example sentences, an original sentence that includes the phrase; an n-gram generating unit adapted to generate n-grams from the original sentence; a likelihood calculating unit adapted to calculate a likelihood that indicates whether the paraphrase sentence input from the paraphrase sentence extracting unit is similar in context to the original sentence input from the original sentence extracting unit based on the n-grams input from the n-gram generating unit and the paraphrase sentence input from the paraphrase sentence extracting unit; a paraphrase extracting unit adapted to extract a paraphrase included in a paraphrase sentence whose likelihood has a value that indicates a higher degree of similarity in context to the original sentence than a threshold value; and a language model generating unit adapted to generate a language model for automatic speech recognition that is based on an n-gram model from the paraphrase extracted by the paraphrase extracting unit and the learning example sentences.