There is provided an authentication device capable of improving an authentication accuracy, in which a finger tilt angle α made by a straight line between the positions at the fingertip abutting portion 6 and the image pickup camera 4 and the finger positioned in the imaging space is detected from a distance D2 (FIG. 5) between the finger positioned in the imaging space and the image pickup camera 4 and the distance D1 (FIG. 5) between the positions at the image pickup camera 4 and the fingertip abutting portion 6. The projection distortion of the corresponding comparative images can be removed according to the difference between the finger tilt angle α and the finger tilt angle α of registration information previously stored at the time of registration.