To provide a paper post-processing device capable of efficiently storing punched chips generated in punching processing.

The paper post-processing device 1 flattens the punched chips accumulated in a chevron shape after falling in a punched chip storage box 5 by reciprocating the punched chip storage box 5, which stores the punched chips generated by the punching processing and falling from a punching processing part, in a punched chip storage part 4 with a flattening mechanism part 10 provided with an elastic body 6 and an electromagnetic induction part 7. Accordingly, the punched chips can be flattened with a simple constitution without pressing the capacity of the punched chip storage box 5. The punched chips can be efficiently recovered and stored.