To provide a paper sheet processing device capable of simply detecting the attachment/detachment of a storage unit for storing paper sheets and a state where the amount of paper sheets has reached a predetermined level and reducing costs.

The paper sheet processing device has: a storage unit 5 which is attachable to/detachable from to a frame and capable of storing the paper sheets; a moving member 53 which moves when the amount of paper sheets stored in the storage unit 5 reaches a predetermined level; and a detection sensor 35 for detecting the movement of the moving member 53. The moving member 53 is supported on the storage unit 5, and is moved by the attachment/detachment operation of the storage unit 5 when the storage unit 5 is not mounted on the frame, so that the detection sensor 35 can detect that the moving member 53 has moved.