1. A voice search device comprising: learning data dividing means for dividing text data to be subjected to a search such as a document into predetermined linguistic units and outputting a result of division; language model generating means for generating a language model for voice recognition based on the result of division; text dictionary generating means for dividing the text data to be subjected to the search such as the document into units, each being smaller than that in the learning data dividing means, to generate a text search dictionary; voice recognition means for using the language model to recognize an input voice and to output a result of voice recognition as a text; matching unit converting means for dividing the result of voice recognition into the same division units as those in the text dictionary generating means and outputting a result of division; and text search means for receiving an output from the matching unit converting means as an input to make a text search by using the text search dictionary.