1. A biometric information processing apparatus comprising: an aligning unit that aligns a hand image in a first vein image that includes a vein pattern of one hand among a right hand and a left hand as seen from one side of a palm side of the hand or a back side of the hand, with a hand image in a second vein image that includes a vein pattern of the other hand among the right hand and the left hand as seen from the other side among the palm side of the hand or the back side of the hand; and a match determining unit that determines a line element, among a plurality of line elements in the first vein image, that matches any of a plurality of line elements in the second vein image.