To prevent much as possible deterioration of electronic components as and facilitate mounting and replacement of the electronic components and increase the padsing dencity of electronic components.

This structure is provided with a substrate section (front panel section) 4, a plurality of side wiring boards 13, 14 which are so located as to face each other at a specified distance with their one ends being connected to the substrate section 4, and a spanned wiring board 15 which is so located as to face the substrate section 4 at a specified distance with its both ends being connected to the side wiring boards 13, 14. A wind tunnel 19 is formed by the substrate section 4, the side wiring boards 13, 14, and the spanned wiring board 15.