A sheet transport device includes a sheet feeding tray, a reading device, a sheet feeding path, a discharge tray, a discharge path, a discharge elevation device, and a movable wall. On the sheet feeding tray, a plurality of sheets are placed. The discharge tray is located on a lower side of the sheet feeding tray, and receive the plurality of sheets. The discharge path delivers the sheet to the discharge tray. The discharge elevation device moves the discharge path up and down. The discharge path includes a discharge outlet that moves up and down, in a range between the sheet feeding tray and the discharge tray, following an up and downward movement of the discharge path. The movable wall is provided between the discharge outlet and the sheet feeding tray, and changes a posture according to the up and downward movement of the discharge path and the discharge outlet.