When an original document is placed on the lift tray, a timer is reset and starts counting a predetermined time (S12). Whether an alignment device is moved to adjust the original documents loaded on the lift tray in, for example, the widthwise direction transverse to the transportation direction is then determined (S13). If a change in the detected width of the original documents is detected (S13 returns Yes), control returns to S12 and the timer is reset and started again (S12). If there is no change in the detected width of the original documents in S13, control waits for the timer set in S12 to time out (S14). If the timer reaches the predetermined time set in S12 (S15 returns Yes), the lift tray is driven up by the lift motor (S16) and rises until the top limit sensor turns on (S17).