A base member 13 is laid in a space portion, which is defined by an instrument panel, in a vehicle width direction over a generally entire width of the vehicle, and a plurality of ducts 15 to 20 are integrally formed with the base member 13. Furthermore, a meter placing portion 23 on which a meter is placed and an air bag placing portion 24 on which an air bag is placed are formed on the base member 13, and a harness placing portion 26 on which a flat harness is placed is also formed on the base member 13 in the vehicle width direction. Accordingly, the base member with which the plurality of ducts are integrally formed is a separate body from the instrument panel. Even in the case where the size of the instrument panel is changed, the base member is not required to correspond to the instrument panel and therefore, the ducts can be commonly used. Moreover, since the base member is formed with ducts each having a closed structure in section, it has a predetermined physical strength. Since this base member is laid in the vehicle width direction over a generally entire width of the vehicle, that portion of the vehicle body where the instrument panel is arranged is increased in physical strength owing to the provision of this base member for the sake of a possible side crush or collision of the vehicle.