An image processing device is provided which can calculate a feature value which contributes to improving accuracy in comparison of fingerprints, etc. This image processing device is provided with an image input unit, a core line image extraction unit, and a core line adding unit. The image input unit inputs an image in which a pattern of curved stripes is formed from ridges. The core line image extraction unit generates a core line image by extracting a core line from said image. The core line adding unit detects a region or ridge having a predefined feature from the core line image and adds a core line to the detected region or ridge.