A blood vessel image input apparatus is provided which is capable of acquiring a high-precision image of blood vessels of a body part, such as a finger, even if the finger is swept at a non-constant speed. The apparatus includes a solid-state line image sensor, a light source for illuminating the inside of the finger with light, an imaging optical system adapted to focus the light, emitted from the light source and passed through the inside of the finger, on the solid-state line image sensor such that a blood vessel image representing a network structure of veins in the finger is formed on the solid-state line image sensor, and a blood vessel image forming unit adapted to form a complete image of blood vessels by connecting a plurality of partial blood vessel images captured by the solid-state line image sensor while sweeping the finger.