Post-processing trimming apparatus and image-forming apparatus

A post-processing apparatus equipped with a trimming apparatus, which carries out a trimming process on an edge of a bundle of sheets, comprising,

• an inserting mechanism which inserts the bundle of sheets into a trimming process section of the trimming apparatus,
• an edge holding member and an edge sustaining member which pinch a vicinity of the edge of the bundle of sheets inserted into the trimming process section,
• a shifting mechanism which changes a relative position between the edge holding member and the edge sustaining member and makes an opening size between the edge holding member and the edge sustaining member variable before a pinching motion, and
• a controller for receiving information about the number of sheets composing the bundle of sheets from an image forming apparatus;
• said controller which controls the shifting mechanism to adjust the opening size depending on the number of sheets composing the bundle of sheets to be trimmed so as to make at least one of the edge holding member and the edge sustaining member stand by while maintaining the opening size before starting of a pinching motion thereof and before the bundle of sheets is inserted into the trimming process section by the inserting mechanism.