Disclosed is a system for authoring metadata that describe multimedia contents. A storage device loads information on a currently edited metadata document so as to describe multimedia contents, and a metadata editor visualizes the loaded metadata document according to a predetermined method, and allows a user to edit the metadata document. A multimedia access reproducer accesses the input multimedia contents to reproduce corresponding multimedia contents, and an inter-media metadata interface links the multimedia access reproducer and the metadata editor to browse contents and effectively edit information relating to a specific interval of multimedia contents. A metadata output device outputs information on the loaded metadata document according to a predefined format.