1. A watermark embedding method that embeds a watermark in a digital image, the method comprising: determining a degree of local image complexity having a large value for texture regions in the image, and having a small value for flat regions and edge portions; and changing complex portions of the image more than low complex degree portions in accordance with the degree of local image complexity to obtain a watermark embedded image; wherein the determining of the degree of local image complexity of the image includes performing the following: obtaining an edge/texture component value image by measuring an edge and a texture region by using a counter which is incremented when a difference between each pixel and adjacent pixels in the input image is equal to or greater than a threshold, dividing the edge/texture component value image into small blocks, obtaining the sum of edge/texture component values in the block for each divided block, determining a texture degree index of the block as a value which is the sum mapped by a predetermined function, and multiplying each edge/texture component value in a divided block by a texture degree index corresponding to the divided block so as to obtain a texture component value image, and wherein the texture component value image is used as the degree of local image complexity for obtaining the watermark embedded image.