1. A vehicle comprising: a speech input device configured to receive speech; a speech recognition device configured to recognize the received speech and output a recognition result of the received speech including a plurality of instruction candidates corresponding to the received speech; and at least one of a display configured to display the plurality of instruction candidates or a speaker configured to output the plurality of instruction candidates, wherein the speech recognition device resets a recognition environment applied to speech recognition and re-recognizes the received speech when a re-recognition instruction is input by a user, excludes the recognition result of the received speech previously output when the re-recognition is performed, and resets the reset recognition environment to an initial value when the re-recognition is completed, wherein the recognition environment includes at least one of an accuracy parameter related to accuracy of speech recognition, a threshold value of a confidence score, or a search range, and wherein the accuracy parameter represents information on the number of search nodes, and accuracy of speech recognition increases as the number of search nodes increases.