A device and method for transcoding digital audio/video streams. Only the video data, from among audio/video data provided in the form of compressed digital streams such as TV broadcast streams, is transcoded, and then the transcoded video data is synchronized with the audio data. To synchronize the transcoded video data with the audio data, original Presentation Time Stamps (PTSs) of the video data before the transcoding are used for the transcoded video data, or new PTSs are used for the transcoded video data and PTSs of the audio data are updated based on the new PTSs. The transcoding and PTS synchronization is performed on the basis of sections having continuous PTS values. Accordingly, degradation of sound quality due to unnecessary audio data transcoding is avoided, while preventing synchronization mismatching between the audio and video data in the transcoding procedure.