In an apparatus for embedding digital watermarks into an image, a watermark embedding region extraction unit extracts an image region to contain watermarks from a wavelet transformed entire image. A watermark generation unit generates a watermark data row to be embedded according to a user's private key. A normalization operation unit normalizes the quantized data value by using a quantization unit into a normalized data value. An inverse quantization inversely quantizes and outputs the normalized data value. A watermark embedment unit embeds a watermark-embedded data value as a corresponding pixel data value into the watermark embedding region, wherein the watermark-embedded data value is obtained by subtracting, from the inversely quantized data value, the watermark data value added prior to the quantization.