The present invention relates to method and apparatus of providing supplementary service information for A/V contents written in a recording medium. This method has a recording medium containing Presentation Language data, which have to be included like as in a digital television signal for supplementary service information in accordance with Advanced TV Enhancement Forum or Digital TV Application Software Environment standard, and reproduces, if a disk reproduction is requested, the Presentation Language data as well as requested A/V data and provides them for a connected external device such as a digital television. As a result, various video information and functions provided with Presentation Language data by a recording medium can be realized at a digital television set being able to accept Presentation Language data.