This invention includes an image quality priority level decision processing unit (40) which evaluates the magnitude of an image quality of each of a plurality of first image data formed from biometric images associated with the same target on the basis of a specific index having the relationship of a monotone function with authentication accuracy of biometric authentication, and outputs each of the first image data upon adding a priority level thereto on the basis of the evaluation result, a first image storage (6, 81) unit which stores each of the first image data having a priority level added thereto from the image quality priority level decision processing unit (40), a second image storage unit (8, 61) which stores second image data used for comparison/collation with the first image data, an image collation unit (7) which compares/collates the second image data stored in the second image storage unit (8, 61) with the first image data stored in the first image storage unit (6, 81) and outputs the comparison/collation result, and a control unit (9) which controls each of the units. The control unit (9) causes the image collation unit (7) to compare/collate the second image data stored in the second image storage unit (8, 61) with the first image data stored in the first image storage unit (6, 81) in accordance with the priority levels, and outputs the comparison/collation result from the image collation unit (7).