A counterfeit coin detection supporting device ejects outside bank notes of the same denominations as preset denominations as specific banknotes out of bank notes inputted from outside. The denominations and the number of bank notes ejected outside are stored in storage (23). Specific bank notes manually judged to be not counterfeit bank notes are inputted again. When the denominations and the numbers of specific bank notes inputted again agree with those stored in the storage (23), the detection of counterfeit bank notes are judged to be normally ended.