To easily sample a fingerprint even a dry finger by forming a superhydrophilic film on a fingerprint sampling surface.

The side of a fingerprint sampling surface 109 of a triangular prism 105 is irradiated with the light of an illuminating element 101, and this light is supplied to a fingerprint pattern P of a finger F placed on the fingerprint sampling surface 109. The irradiating light contains information of the fingerprint pattern P and this light containing information is totally reflected on the prism 105 and optically taken through an optical lens-barrel 106 into an imaging device 107 as reflected light. In such a device, for example, optical catalytic superhydrophilic films 50 are formed on the fingerprint sampling surface 109 of the prism 105 and preferably on an inner prism surface 40 respectively. Thus, moisture in air easily sticks on the fingerprint sampling surface 109 and the inner prism surface 40 and even when the finger F to sample the fingerprint is dry, the fingerprint pattern of that finger F can be closely adhered to the fingerprint sampling surface 109 while using the superhydrophilic films 50.