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, implemented by a processor, 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, prevents the language model score look-ahead values from concentrating on the beginning of the word by distributing the language model score look-ahead value corresponding to the phoneme at the beginning of the word to one or more phoneme that are not at the beginning of the word, and obtains an updated language model score look-ahead value at each of the phoneme based on the distribution.