A method for embedding a watermark into a digital image. The method includes independently changing real number components and imaginary number components of each of coefficient values of a complex watermark coefficient matrix using a key, from the watermark to be embedded in the digital image. The method further includes a step for performing a discrete Fourier inverse transform on the sequence matrix of the changed watermark and generating a watermark pattern. The method also includes a step for adding like tiling the water mark pattern to the original image, and generating an embedded image.