In verification of image data of a captured image as to whether it is original one, the verification is possible even for image data subjected to a peripheral illumination correction or an exposure correction. An order information calculation unit selects a pixel set including two or more pixels based on pixel values and information on an image space of image data of a captured image, and calculates an order of magnitude between pixels in the selected pixel set. A verification data producing unit generates verification data used in verification of whether the image data has not been tampered with, based on the calculated order of magnitude. An image output unit outputs the image data and the verification data.