The position of blood vessels can be more appropriately specified by means of appropriately selecting, on the basis of the conditions and components utilized, and angle between a light emitting unit optical axis of a near-infrared light emitting unit and a normal light of an irradiated surface, and angle between an optical axis of a light receiving side lens and the normal line of the irradiated surface, and an angle between a light receiving surface of a photo diode array and the light receiving unit optical axis. Thus, the subcutaneous blood vessel depth in the direction of the normal line from the irradiated surface can be specified based on changes in illumination intensity in a photodiode array. Consequently, the position of subcutaneous blood vessels can be easily specified.
