According to one embodiment, a sheet processing apparatus includes: a paper feeding section configured to receive a sheet and feed the sheet; a detecting section configured to detect the fed sheet; a standby tray on which the fed sheet is stacked, the standby tray including a first roller configured to convey the sheet; a second roller 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 according to a result of the detection during conveyance of the sheet to the standby tray.