1. An utterance verification method for an isolated word N-best speech recognition result, comprising: calculating log likelihoods of a context-dependent phoneme and an anti-phoneme model based on an N-best speech recognition result for an input utterance; measuring a confidence score of an N-best speech-recognized word using the log likelihoods; calculating a distance between phonemes for the N-best speech-recognized word; comparing the confidence score with a threshold and the distance with a mean of distances; and accepting the N-best speech-recognized word when the compared results for the confidence score and the distance correspond to acceptance, wherein the log likelihood of the context-dependent phoneme is calculated by: 
 log likelihood of context-dependent phoneme={(log likelihood of current phoneme)−(mean of base phonemes of current phoneme)}/(standard deviation of base phonemes of current phoneme).