1. A personal identification apparatus comprising: a light source stored in said personal identification apparatus; a window, provided on a surface of said personal identification apparatus, for transmitting light from the light source; an imaging unit which captures the light transmitted through a finger, which is to be captured, and irradiated on the finger through said window; and an image processing unit which extracts a vessel pattern of the finger for personal identification from an image which is captured by said imaging unit and which includes joint parts of the finger, wherein an amount of irradiated light of the light source is controlled in accordance with transmittance for each part of the finger based on position information on the joint parts of the finger extracted from information on the transmittance of the image captured by said imaging unit, and said image processing unit extracts the vessel pattern of the finger for personal identification from the image captured in accordance with the amount of the controlled irradiated light.