1. An electronic watermark editor of a compressed video with an electronic watermark that expresses information by a relative difference between two DCT coefficient values embedded in a pair, comprising: a means for specifying a template to instruct on a block position used for a video when embedding the electronic watermark; a means for providing an electronic watermark editing bit to be newly embedded; a means for detecting a coefficient value pair bit embedded in the pair of DCT coefficient values of a block instructed by the template; and a means for comparing the detected coefficient value pair bit with the editing bit to be newly embedded and embedding the editing bit only when the detected coefficient value pair bit and the editing bit to be newly embedded are different.