A paper sheet processing apparatus capable of correcting an inclination to a traveling direction when a paper sheet is inserted into an insertion slot. The paper sheet processing apparatus includes a pair of movable pieces capable of being moved toward a center direction of the traveling route through which the paper sheet is conveyed by a motor. The pair of movable pieces are moved toward the center direction of the traveling route by a driving source such that the distance between one movable piece and the other movable piece becomes shorter than a width of the bill and corrects the inclination of the bill to the traveling direction by regulating side edges of the bill to be conveyed before the bill reaches the movable pieces.