A speech recognition apparatus arranged in a vehicle, the apparatus comprising: a camera configured to capture a user image; a microphone; a memory configured to record an audio signal input through the microphone; a speech recognition unit configured to recognize a speech of the user from an effective speech signal, and a control unit configured to receive through the camera the user image; track eyes of a user from the user image, through the camera; determine whether the eyes of the user are directed toward the microphone; if it is determined that the eyes of the user are directed toward the microphone, operate the speech recognition unit and determine whether a nonlexical word exists in the audio signal, wherein the audio signal is recorded in the memory from a point of time at which the user is directed toward the microphone; if the nonlexical word is detected from the recognized audio signal, determine, as the effective speech signal, a speech signal following the detected nonlexical word, and recognize the effective speech signal through the speech recognition unit; and if the nonlexical word is not detected from the speech signal input through the microphone, turn off the speech recognition unit, wherein the control unit is configured to determine whether the nonlexical word exists by operating the speech recognition unit and detecting the nonlexical word through the speech recognition unit from the audio signal during a preset time from the point of time at which the user is directed toward the microphone. a camera configured to capture a user image; a microphone; a memory configured to record an audio signal input through the microphone; a speech recognition unit configured to recognize a speech of the user from an effective speech signal, and a control unit configured to receive through the camera the user image; track eyes of a user from the user image, through the camera; determine whether the eyes of the user are directed toward the microphone; if it is determined that the eyes of the user are directed toward the microphone, operate the speech recognition unit and determine whether a nonlexical word exists in the audio signal, wherein the audio signal is recorded in the memory from a point of time at which the user is directed toward the microphone; if the nonlexical word is detected from the recognized audio signal, determine, as the effective speech signal, a speech signal following the detected nonlexical word, and recognize the effective speech signal through the speech recognition unit; and if the nonlexical word is not detected from the speech signal input through the microphone, turn off the speech recognition unit, receive through the camera the user image; track eyes of a user from the user image, through the camera; determine whether the eyes of the user are directed toward the microphone; if it is determined that the eyes of the user are directed toward the microphone, operate the speech recognition unit and determine whether a nonlexical word exists in the audio signal, wherein the audio signal is recorded in the memory from a point of time at which the user is directed toward the microphone; if the nonlexical word is detected from the recognized audio signal, determine, as the effective speech signal, a speech signal following the detected nonlexical word, and recognize the effective speech signal through the speech recognition unit; and if the nonlexical word is not detected from the speech signal input through the microphone, turn off the speech recognition unit, if the nonlexical word is detected from the recognized audio signal, determine, as the effective speech signal, a speech signal following the detected nonlexical word, and recognize the effective speech signal through the speech recognition unit; and if the nonlexical word is not detected from the speech signal input through the microphone, turn off the speech recognition unit, wherein the control unit is configured to determine whether the nonlexical word exists by operating the speech recognition unit and detecting the nonlexical word through the speech recognition unit from the audio signal during a preset time from the point of time at which the user is directed toward the microphone.