A speech search method for a display device is discussed. The method includes the steps of outputting media data, receiving a speech search command from a user, and determining whether the speech search command includes a query term. If the speech search command does not include a query term, the method further comprises the step of extracting a query term which is full and searchable from audio data of the media data which is outputted immediately prior to the speech search command. Finally, the method includes the step of performing a speech search using the extracted query term.