A banknote processing apparatus, comprising: an upper unit including a depositing unit, a transport unit, a banknote recognition unit and a control unit, the depositing unit being configured to deposit a banknote in the banknote processing apparatus, the transport unit having a loop-shaped transport path, the banknote recognition unit being provided on the transport unit and configured to recognize the banknote deposited from the depositing unit, the control unit being configured to control a whole of the banknote processing apparatus, and a lower unit being below the upper unit and including a temporary storage unit and a safe, the temporary storage unit being configured to temporarily store therein the banknote recognized by the banknote recognition unit, the safe housing a transport module and a banknote storage unit (18a-18e) therein, the banknote storage unit (18a-18e) being configured to store the banknote stored in the temporary storage unit, wherein the banknote storage unit (18a-18e) comprises a plurality of detachable storage units (18a-18e) at least one of which is a storage unit having an upper storage unit and a lower storage unit in a vertical direction and having an opening in a side surface in each of the upper storage unit and the lower storage unit, the upper and lower storage units being configured to store a banknote therein transported from the transport module and to feed out the stored banknote from each opening to the transport module, and the transport module has a transport path configured to connect the upper storage unit and the lower storage unit of the storage unit having the upper and lower storage units and the transport unit, wherein the transport module is detachable from the safe, characterized in that the transport module and the storage unit having the upper storage unit and the lower storage unit are configured to replace any two adjacent storage units (18a-18e) so that the transport module is positioned adjacent to the side surface of the storage unit having the upper storage unit and the lower storage unit. an upper unit including a depositing unit, a transport unit, a banknote recognition unit and a control unit, the depositing unit being configured to deposit a banknote in the banknote processing apparatus, the transport unit having a loop-shaped transport path, the banknote recognition unit being provided on the transport unit and configured to recognize the banknote deposited from the depositing unit, the control unit being configured to control a whole of the banknote processing apparatus, and a lower unit being below the upper unit and including a temporary storage unit and a safe, the temporary storage unit being configured to temporarily store therein the banknote recognized by the banknote recognition unit, the safe housing a transport module and a banknote storage unit (18a-18e) therein, the banknote storage unit (18a-18e) being configured to store the banknote stored in the temporary storage unit, wherein the banknote storage unit (18a-18e) comprises a plurality of detachable storage units (18a-18e) at least one of which is a storage unit having an upper storage unit and a lower storage unit in a vertical direction and having an opening in a side surface in each of the upper storage unit and the lower storage unit, the upper and lower storage units being configured to store a banknote therein transported from the transport module and to feed out the stored banknote from each opening to the transport module, and the transport module has a transport path configured to connect the upper storage unit and the lower storage unit of the storage unit having the upper and lower storage units and the transport unit, wherein the transport module is detachable from the safe, characterized in that the transport module and the storage unit having the upper storage unit and the lower storage unit are configured to replace any two adjacent storage units (18a-18e) so that the transport module is positioned adjacent to the side surface of the storage unit having the upper storage unit and the lower storage unit.