the cpu 63 determines that only a damaged portion is present in the paper sheet fig1 demonstrates a dog ear or bent edge determination system in detail the detection lengths ranges used for detecting the dog ears number four in the preferred embodiment as shown in fig1 these detection lengths are indicated by lengths x and y respectively in the directions perpendicular and parallel to the feeding direction the length x corresponds to the first and third lengths a1 and a3 widths adjacent to the dog ear detection areas are obtained by equation 3 if the measured widths fall within the allowable range the obtained values w i1 w i3 w m1 and w m3 are stored in the memory however if the measured widths do not fall within this range that is if the widths are short due to the presence of a damaged portion or puncture these values are not stored when the resolution of the line sensor in the feeding direction is 1 mm y 16 mm a standard area s f1 is selected in a portion spaced apart from the leading edge of the paper sheet p by the length y i 20 mm in fig1 only when widths measured from the position spaced apart from the leading edge of the paper sheet by 20 mm fall within the allowance 16 values.