The invention is to precisely extract a digital watermark from image data which are subjected to embedding of the digital watermark in a state of a binary image and are then converted into a multi-value image (gray scale image).For attaining the foregoing object, a digital watermark extracting apparatus for extracting a digital watermark for example in an original includes an acquiring unit for acquiring multi-value image data obtained by reading the original with a predetermined reading unit, a pre-processing unit for selecting one of plural threshold values and binarizing the multi-value image data with the selected threshold value, and an extracting unit for extracting the digital watermark from image data binarized in the pre-processing unit, wherein selection of the threshold value, binarization an extraction of the digital watermark are repeated to obtain an optimum extraction result of the digital watermark.