1. A voice recognition apparatus comprising: a context model created by modeling recognition target context; a model creator configured to classify the recognition target context according to a length of syllables, and to create a context model for each length of syllables; and a voice recognizer configured to create a candidate group corresponding to a received voice signal based on an acoustic model and the context model for each length of syllables, calculate a length of a user's speech based on a Begin of Speech (BoS) and an End of Speech (EoS), and apply a high reliability weight value to a candidate having a length of syllables corresponding to the length of speech.