Abstract: A flat pre-board plate including connection electrodes, internal interconnections, and external-connection portions is prepared. This pre-board plate is cut at portions each located between adjacent ones of the connection electrodes, thereby forming trenches. A plurality of semiconductor elements are placed in each of the trenches. Electrode pads and the connection electrodes are connected to each other by metal wires. Transparent lids are placed on, and bonded to, spacers to cover the semiconductor elements. Thereafter, two lines of the connection electrodes arranged between adjacent ones of the trenches are separated from each other. Subsequently, adjacent ones of the semiconductor elements are also separated from each other.