A sheet bundle conveying device includes a tray device on which sheets are placed and held in a bundle, a sheet bundle conveying path along which a sheet bundle from the tray device is guided to a predetermined processing position, a grip transferring device located on the sheet bundle conveying path for gripping and transferring the sheet bundle from the tray device to a processing position, and a grip controlling device for controlling the grip transferring device. When an apparatus error occurs, the grip transferring device moves the conveyed sheet bundle backward to the collection stage. A grip on the sheet bundle is released on the collection stage after the sheet bundle is returned.