1. A speech recognizing device comprising: natural speech recognizing means for recognizing speech input in an application program by dictation; and recognition result converting means for converting a recognition result from said natural speech recognizing means into a final recognition result processable by said application program on the basis of a grammar to be used for recognizing said input speech in a grammar method, wherein said recognition result converting means further comprises: candidate sentence generating means for evolving said grammar to generate candidate sentences that are candidates for said final recognition result; and matching means for selecting a candidate sentence as said final recognition result among the candidate sentences by matching said candidate sentences generated by said candidate sentence generating means against the recognition result by said natural speech recognizing means, and wherein the candidate sentence comprises a sentence having an associated highest score calculated according to the formula: (ngramWords—replacedWords—rejectedWords—insertedWords)/ngramWords wherein “ngramWords” comprises a first number of words contained in an N-gram recognition result, “replacedWords” comprises a second number of words that have been replaced with different words for the N-gram recognition result, “rejectedWords” comprises a third number of words that are contained in the N-gram recognition result but not in the candidate sentences, and “insertedWords” comprises a fourth number of words that are not contained in the N-gram recognition result but are contained in the candidate sentences.