Sheet processing apparatus

A sheet processing apparatus, comprising:

• a pushing member for pushing a portion of a sheet bundle to be folded, to thereby fold the sheet bundle;
• a drive device configured to move the pushing member;
• a first conveyance unit having a roller pair which conveys the sheet bundle folded by the pushing member, wherein the roller pair can be separated;
• a second conveyance unit provided on a downstream side of the first conveyance unit and configured to convey the sheet bundle;
• a first detection unit configured to detect an amount by which the pushing member is moved by the drive device;
• a second detection unit configured to detect an amount by which the sheet bundle is conveyed by the first conveyance unit;
• and
• a control unit configured to separate the roller pair based on the amount which is detected by the first detection unit and the amount which is detected by the second detection unit.