A paper sheet binding die set comprises first and second dies, each having an opposed surface comprising a plurality of tooth portions. The first and second dies face each other such that the first die and the second die are capable of meshing with each other. Each tooth portion of the first die comprises a valley-bottom portion, and a peak-top portion. Each tooth portion of the second die comprises a valley-bottom portion, a peak-top portion, and an inclined-surface portion extending at an incline from the valley-bottom portion to the peak-top portion. The peak-top portion of each of the plurality of tooth portions of the first die has a length so as to cover the inclined-surface portion of the corresponding tooth portion of the second die upon meshing of the first and second dies. The first and second dies pressurize the plurality of stacked paper sheets to bind them together.