The present invention relates to a method for embedding and detecting a watermark where a forgery/alternation of an image can be identified and the location of forgery/alternation can be verified by embedding and detecting a watermark into a digital image which is shot in real time. The watermark is generated by using a quantized coefficient after frequency transform used in the compression process. By embedding this into an image, the image can be compressed simultaneously with the embedded watermark. The present invention relates to a method for embedding a robust watermark which embeds a random sequence circular shifted from an original pseudo random sequence by the distance d as the watermark is embedded into an image, and a method for generating and embedding the watermark by using a DCT coefficient quantized during an MPEG compression process of the image.