1. A biometric authentication device, comprising: an operation panel configured to input identifying information of a user; a camera configured capture an image of a user's hand a plural number of times; and one or more processors configured to: extract vein information, on a per image basis, of the hand image captured by the camera and execute a matching process of matching the vein information with previously-provided vein data associated with the identifying information; acquire determination data specifying, based on a thickness of a vein in a predetermined position in the hand image, whether the hand image is acquired by capturing a living organism or not; and authenticate the user when a matching result of the matching on the per hand-image basis demonstrates its normality and the determination data demonstrates that the hand image is acquired by capturing the living organism, or does not authenticate the user.