1. A fingerprint data registering method, comprising: blurring a fingerprint-shaped pseudo image and displaying the blurred pseudo image; extracting a fingerprint position of a fingerprint image acquired for authentication registration; determining a position in the pseudo image, which corresponds to the extracted fingerprint position; converting a part of the blurred pseudo image at the corresponding position to a clear partial pseudo-image having a higher resolution than that of the blurred pseudo image and displaying the clear partial pseudo-image; and registering the acquired fingerprint image as an authentication-purpose fingerprint image in association with said converting and displaying.