1. An organism characteristic data acquiring apparatus for acquiring organism characteristic data, for at least one of registration organism characteristic data storage and an authentication unit for authenticating the identification object person, from an identification object person or a registration object person to authenticate the identification object person based on the organism characteristic data, comprising: a sampling section for successively sampling partial images of a portion of an organism from each of the identification object person and/or the registration object person, each sampled partial image having an overlapping portion shared with a previously sampled partial image sampled immediately before the sampled partial image; a detection section for detecting, substantially contemporaneously and subsequent to obtaining the sampled partial image by said sampling section, a relative positional relationship between the sampled partial image and the previously sampled partial image based on the overlapping portion; an extraction section for extracting, substantially contemporaneously and subsequent to detection of the relative positional relationship by said detection section, characteristic portion data including characteristic information unique to the organism portion from the sampled partial image; and a synthesis section for synthesizing, substantially contemporaneously and subsequent to extraction of the characteristic portion data by said extraction section, the characteristic portion data of the sampled partial image extracted by said extraction section and characteristic portion data of the previously sampled partial image based on the relative positional relationship of the sampled partial image detected by said detection section and outputting a result of the synthesis as organism characteristic data of the portion of the organism for the at least one of registration organism characteristic data storage and an authentication unit for authenticating the identification object person using sampled partial images forming less than an entire image of the portion of the organism sampled in said sampling.