The present invention relates to a paper money stopper in an ATM (Automated Teller Machine), capable of preventing jam of bank notes which may occur due to incorrectly stacked paper money, by guiding the bank notes to be loaded in a neat and orderly manner in a paper money storage area in temporary storage, the paper money being stacked in the temporary storage via a split stack unit from a conveyor route in the ATM. To accomplish this, there is provided a paper money stopper in an ATM arranged at the rear side wall of a temporary storage to prevent slipping of the bank notes as they are stacked and input to the temporary storage, the stopper comprising: fixed plates arranged vertically side by side on both sides of the rear side wall of the temporary storage; a transverse slot, which is engraved in the transverse direction outside the fixed plates on both sides and receives a front end portion of paper money being conveyed to thus adjust paper money input in a horizontal state; and a damper disposed in the vicinity of the transverse slot, for preventing a slipping motion of paper money being input as well as for decreasing the speed of paper money being input.