Abstract: A processor obtains characteristics information of a biometric image captured while casting first or second illumination light onto an authentication target. The first illumination light includes light of a first wavelength, and the second illumination light includes light of the first wavelength and light of a second wavelength. The processor reads characteristics information of a biometric image captured while casting illumination light cast onto the authentication target from a memory that stores first characteristics information of a first biometric image and second characteristics information of a second biometric image. The first biometric image is captured while casting the first illumination light onto a registration target, and the second biometric image is captured while casting the second illumination light onto the registration target.