A vein authentication device according to the present invention includes an imaging part for continuously imaging a portion of venation present inside a finger by near-infrared light scattered inside the finger by irradiating a finger surface with the near-infrared light while continuously imaging a portion of fingerprints present on the finger surface or inside the finger by reflected light reflected on the finger surface or inside the finger, a motion vector detection part for detecting a motion vector of the fingerprints, an image synthesis part for synthesizing images picking up a portion of the fingerprints to generate an image of the fingerprints and synthesizing images picking up a portion of the venation to generate an image of the venation, a vein pattern extraction part for extracting a vein pattern from the image of the venation, and an authentication part for performing authentication processing.