A primary object of the present invention is to extract a difference in shading of a blood vessel image in a picked up image as information to be used for authentication, and to acquire a larger number of pieces of biometric information from one image. An individual authentication device to be used to authenticate an individual using feature information of a vascular pattern acquired from a living body includes an imaging unit that images a region of the living body serving as an object of authentication, and an arithmetic unit that acquires the picked up image as an authentication image. The arithmetic unit extracts a vascular pattern from the authentication image, and acquires a degree of shading of the vascular pattern as the feature information.