Sheet processing apparatus and sheet conveying method

A sheet processing apparatus comprising:

• a paper feeding section configured to receive a sheet conveyed from an apparatus at a preceding stage and feed the sheet;
• a detecting section configured to detect the sheet fed by the paper feeding section;
• a standby tray on which the sheet fed by the paper feeding section is stacked, the standby tray including a first roller configured to convey the sheet;
• a second roller located above the standby tray and configured to pivot to come into contact with and separate from the first roller;
• a processing tray on which the sheet dropped and supplied from the standby tray is stacked, the processing tray holding the sheet while requested processing is applied to the sheet;
• a paper discharge section configured to receive the sheet subjected to the processing and discharged from the processing tray;
• and
• a control section configured to separate the second roller from the first roller at predetermined timing according to a result of the detection by the detecting section during conveyance of the sheet to the standby tray.