To facilitate refilling of binders in a binding device for performing treatment for mounting split ring type binders to paper.

A service door 4 provided at the side face of a cartridge storage part is turnable from a vertical closed position into a horizontal position around a lower part used as a fulcrum, and opened horizontally to pull out a binder cartridge 21 onto the door. A presser plate 6 is suspended through a pantograph 5 from the upper part of the binder cartridge storage part. The presser plate presses down the binders in the cartridge. A lifting arm 11 mounted to a frame is connected to the lower end of the door by a link 12 to interlock the door and the lifting arm. When opening the door, the lifting arm is lifted to push the pantograph and presser plate upward, and the cartridge can be pulled out to load the binders. When returning the cartridge and closing the door, the presser plate is lowered to press down the binders in the cartridge.