Paper handling apparatus and method therefor

A bill handling apparatus having a thickness detection sensor 401 for detecting the thickness of bills; optical sensors 405 and 406 for acquiring images of the profiles and surfaces of the bills; a judgment unit for judging the positions and directions of folds of the bills with the use of signals obtained with the thickness detection sensor 401 and the optical sensors 405 and 406; and a control unit for exercising control such that if a judgment result of the judgment unit shows that the position and direction of a fold of a folded bill are unlikely to cause double bill transfer during bill transfer by considering the relationship of the folded bill to a bill located immediately before or after the folded bill, the folded bill is kept in the apparatus without being returned to the user.