A biometric authentication apparatus comprising: an obtainment unit configured to obtain biometric characteristics information of a first authentication-target living-body image captured while casting first illumination light in a long wavelength band of 700 nm or longer onto a living body that is an authentication target and biometric characteristics information of a second authentication-target living-body image captured while casting second illumination light including light of the first illumination light and light in a short wavelength band of 600 nm or shorter onto the living body that is the authentication target; a reading unit configured to read first biometric characteristics information of a first biometric image captured while casting the first illumination light onto a living body that is a registration target and second biometric characteristics information of a second biometric image captured while casting the second illumination light onto the living body that is the registration target from a storage unit that stores the first biometric characteristics information and the second biometric characteristics information; a calculation unit configured to calculate a first similarity between the biometric characteristics information of the first authentication-target living-body image and the first biometric characteristics information, a second similarity between the biometric characteristics information of the first authentication-target living-body image and the second biometric characteristics information, a third similarity between the biometric characteristics information of the second authentication-target living-body image and the first biometric characteristics information, and a fourth similarity between the biometric characteristics information of the second authentication-target living-body image and the second biometric characteristics information; and an authentication unit configured to conduct authentication of the living body that is the authentication target on the basis of the first similarity, the second similarity, the third similarity and the fourth similarity. an obtainment unit configured to obtain biometric characteristics information of a first authentication-target living-body image captured while casting first illumination light in a long wavelength band of 700 nm or longer onto a living body that is an authentication target and biometric characteristics information of a second authentication-target living-body image captured while casting second illumination light including light of the first illumination light and light in a short wavelength band of 600 nm or shorter onto the living body that is the authentication target; a reading unit configured to read first biometric characteristics information of a first biometric image captured while casting the first illumination light onto a living body that is a registration target and second biometric characteristics information of a second biometric image captured while casting the second illumination light onto the living body that is the registration target from a storage unit that stores the first biometric characteristics information and the second biometric characteristics information; a calculation unit configured to calculate a first similarity between the biometric characteristics information of the first authentication-target living-body image and the first biometric characteristics information, a second similarity between the biometric characteristics information of the first authentication-target living-body image and the second biometric characteristics information, a third similarity between the biometric characteristics information of the second authentication-target living-body image and the first biometric characteristics information, and a fourth similarity between the biometric characteristics information of the second authentication-target living-body image and the second biometric characteristics information; and an authentication unit configured to conduct authentication of the living body that is the authentication target on the basis of the first similarity, the second similarity, the third similarity and the fourth similarity.