Paper handling apparatus and method therefor

A bill handling apparatus having a thickness detection sensor for detecting the thickness of bills; optical sensors and 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 and the optical sensors and ; 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.