PURPOSE: To shorten a wiring length between modules and to prevent wiring from crossing each other among layers by arranging pin assignment in first and second connectors inversely and by arranging wirings of an electronic part approximately parallel between connectors on first and second sub- substrates.

CONSTITUTION: Pin assignment in a first connector 16a and pin assignment in a second connector 16b are constituted to be inverse each other and wirings 19a, 19b between modules 11a, 11b are made approximately parallel on a main board 15. In each of sub-substrates 14a, 14b of the first and second modules 11a, 11b, electronic parts 13a, 13b are arranged so that a plurality of wirings 19a, 19b are approximately parallel between the electronic parts 13a, 13b and the connectors 16a, 16b. Thereby, the wirings 19a, 19b do not cross each other in any of the main board 15 and the sub-substrates 14a and 14b and a pair of modules 11a, 11b can be packaged in opposed positions.