According to one embodiment, a speech processing device includes an utterance error occurrence determination information storage unit that stores utterance error occurrence determination information; a related word information storage unit that stores related word information including words; an utterance error occurrence determining unit that compares each of the divided words with the condition, gives the error pattern to the word corresponding to the condition, and determines that the word which does not correspond to the condition does not cause the utterance error; and a phoneme string generating unit that generates a phoneme string of the utterance error. The one of the error patterns associated with one of the conditions is the speech error, the utterance error occurrence determining unit further gives an incorrectly spoken word from the related word information, and the phoneme string generating unit generates a phoneme string of the incorrectly spoken word.