To reduce noise generated when a binding member moves.

This post processing device comprises a drive control means for moving a moving binding device 66 at acceleration a satisfying a≤(g×L)/h, where g is the gravity acceleration component, L is the distance from one guided member 71 to the center 66 of gravity in the direction perpendicular to the direction of the gravity acting on the center 66a of gravity of the moving binding device 66, h is the distance between the one guided member 71 and a contact position between a drive member 73 and a guide member in the direction of the force acting at the contact position during the driving of the drive member 73, and a is the acceleration during the movement of the moving binding device 66.