Sheet trimming apparatus and image forming system

A sheet trimming apparatus comprising:

• a trimming section provided with a trimming cutter blade for trimming a sheet bundle;
• a paper scrap container for storing paper scraps separated from the sheet bundle by the trimming cutter blade;
• and
• a paper scrap guide member made of a flexible member, which is provided to create, under the trimming section, a falling space through which the paper scraps are made to fall from the trimming section to the paper scrap container, wherein the falling space is formed between the paper scrap guide member and a wall member opposed to the paper scrap guide member;
• a shutter temporarily stacking the paper scraps on the shutter above the paper scrap container when the shutter is closed and dropping the temporarily stacked paper scraps into the paper scrap container when the shutter is opened, and on a surface of the shutter the paper scrap guide member being connected;
• wherein when the shutter is closed the paper scrap guide member is pushed by the shutter to assume a first state of being bent for significantly expanding a gap of the falling space between the paper scrap guide member and the wall member, and when the shutter is opened the paper scrap guide member is pulled by the shutter to assume a second state of narrowing the gap and creating an inclined flat surface for guiding the paper scraps to fall.