In a sheet processing apparatus that performs processing for sheets after image formation such as sorting or stapling of the sheets, when the sheets are subjected to processing in a processing tray, after the sheets are discharged to the waiting tray, a paddle operation is started to drop the sheets to the processing tray. When the paddle is in a position where the paddle does not come into contact with the sheets on the processing tray, the rotation of the paddle is stopped once to prevent the paddle from interfering with the sheets.