A compact and highly accurate downward irradiation type finger vein authentication device achieved by providing a structure that stabilizes the finger and also prevents adverse effects caused by the left and right fingers. The finger vein authentication device comprises a center finger stand for mounting the finger for authentication; a light source for irradiating infrared light onto the finger; an image capture unit for capturing an image of the finger veins by way of light from a light source; an aperture to open in the image capture direction of the image capture unit; a storage device to store the finger biological information; an authentication processor unit to extract the features from the image captured by the image capture unit and match the features with the biological information stored in the storage device; and a left and right finger stand for the fingers on the left and right of the finger for authentication. This left and right finger stand is installed at a position somewhat higher than the center finger stand. This left and right finger stand is also made from a light blocking member and a light source is installed in the lower section.