A perfect non-contact type vein authentication apparatus is provided with a light source for emitting infrared light; an input interface equipped with an imaging unit for photographing a vein image of a living body by the infrared light emitted from said light source; a unit for controlling intensity of light to be illuminated; an image calculating unit for performing a feature extracting operation and a feature authenticating operation with respect to an image; and a positioning unit for presenting the living body. More specifically, the light source is provided in front of the living body. Both the light source and the imaging unit are installed in such a positional relationship that the light of the light source gives no adverse influence to the imaging unit. Also, the light source is installed in such a direction that the light of the light source gives no adverse influence to the imaging unit.