In a finger vein authentication unit and an information processing unit using the same, in order to realize a reduction in size and maintain high accuracy such that the finger vein authentication unit is applied to a small-sized information processing unit such as a mobile telephone, the finger vein authentication unit includes a light source which irradiates infrared light to a finger, an imaging sensor which images a vein image by the light which is diffused in the finger and transmitted through the front side of the finger, and an image processing unit which processes the image. The light source is mounted on the front side of the finger and emits the light toward the side surfaces of the finger. Further, a wall is disposed on either side of the finger vein authentication unit for supporting the finger and guiding the irradiated infrared light.