1. A speech recognition apparatus which calculates, per path, a cumulative score of a language score, a word acoustic score and a garbage acoustic score and outputs a word string with a highest cumulative score as a recognition result of an unidentified input speech including a non-language speech, the speech recognition apparatus comprising: a garbage acoustic model storage unit operable to store, in advance, a garbage acoustic model which is an acoustic model learned from a collection of unnecessary words; a feature value calculation unit operable to calculate a feature parameter necessary for recognition by acoustically analyzing the unidentified input speech per frame which is a unit for speech analysis; a garbage acoustic score calculation unit operable to calculate the garbage acoustic score by comparing the feature parameter and the garbage acoustic model per frame; a garbage acoustic score correction unit operable to correct the garbage acoustic score calculated by the garbage acoustic score calculation unit so as to raise said score in the frame where the non-language speech is inputted; and a recognition result output unit operable to output the word string as the recognition result of the unidentified input speech, said word string having the highest cumulative score of the language score, the word acoustic score, and the garbage acoustic score corrected by the garbage acoustic score correction unit.