Abstract: A paper sheet stacking mechanism 50 includes a stacking wheel 52, a roller 54 that is disposed outward from the stacking wheel 52 so as to be coaxially aligned with the stacking wheel 52 and that is rotatable about a shaft 53 at a greater angular velocity than that of the stacking wheel 52, and a transport unit that is configured to transport a paper sheet to the gap between two adjacent vanes 52b of the stacking wheel 52. The transport unit is located such that a discharge position is disposed outward from the outer periphery of the base 52a of the stacking wheel 52 and inward of the circular region defined by the tips of the vanes 52b of the stacking wheel 52 during the rotation of the stacking wheel 52, when viewed in the axial direction of the shaft 53 of the stacking wheel 52.