1. A language model score look-ahead value imparting device that comprises: a word dictionary that defines a phoneme string of a word; a language model that imparts a score of appearance easiness of a word; and a smoothing language model score look-ahead value calculation unit that obtains a language model score look-ahead value at each phoneme in the word from the phoneme string of the word defined by the word dictionary and the score defined by the language model so that the language model score look-ahead values are prevented from concentrating on the beginning of the word.