PURPOSE: To eliminate an application of an excess load to a rotary shaft for supporting a rotary cam in a sheet binding device for binding stuck placed sheets.

CONSTITUTION: A slider 8 mounted in a movable state at a bracket 5 is operated by a cam 3c to operate a tip bending unit 9. Another cam 3b is engaged with a slider block for operating a stapler 17. Cams 3a, 3b, 3c are designed to that two parts radially opposed of the different cams 3a, 3b, 3c simultaneously generate effects relative to a journal 3d. Accordingly, an operating force in one direction generated by the one cam 3b or 3c is canceled by a reaction force of an opposite direction of the same magnitude generated by the other cam 3a or 3b.