A circular image (A1) of a to-be-examined coin (A0) is picked up by a CCD sensor unit (11). The circular image (A1) of the to-be-examined coin (A0) is transformed into a rectangular image (B1) by a transformation processing means (142). On the other hand, a rectangular image (B) of a master coin (A) used as a criterion is prestored in a master-image memory (148). When the circular image (A1) of the to-be-examined coin (A0) is transformed into the rectangular image (B1) by the transformation processing means (142), the rectangular image (B1) is compared with the rectangular image (B) stored in the master-image memory (148) by a comparison means (144). If both of the rectangular images (B1, B) do not coincide substantially with each other, a part of the rectangular image (B1) of the to-be-examined coin is moved from an end thereof to an opposite end by an alignment means (143) so as to generate a new rectangular image (B2) through a shift conversion. If both of the rectangular images (B1, B) coincide with each other, it is judged that the to-be-examined coin (A1) is a genuine coin. If any one of the rectangular images of the to-be-examined coin does not coincide substantially with the rectangular image (B) of the master-image memory (148), it is finally judged that the to-be-examined coin (A0) is a spurious coin.