A forensic mark insertion apparatus includes: an original content segment storage unit for storing multiple original contents; and a service control unit for, in response to a request for a content from a user, retrieving an original content corresponding to the request for the content from the original content segment storage unit, separating the retrieved original content into plurality of content segments, selectively inserting a forensic mark into some of the content segments, and assembling the content segments to produce an forensic-mark inserted content to be provided to the user.