An image reading apparatus includes a supply tray which supports sheets and includes a movable plate configured to move in correspondence to reduction in a number of the sheets, a discharge tray which is located below the supply tray; a discharge unit which has a discharge opening for discharging the sheet and moves from a lower position and a higher position in correspondence to reduction in the number of the sheets supported on the supply tray, a controller which controls movements of the movable plate and the discharge unit, and a sheet detection unit which detects whether the sheets supported on the discharge tray is lower than a predetermined height. The controller determines a timing to move the discharge unit from the higher position toward the lower position based on a detection result of the sheet detection unit.