To secure the extent of sufficient rigidity against various kinds of inputting without increasing weight and cost.

A closed cross-sectional instrument panel structural body 3 is made up into a form where an air conditioner consisting of a heater core 11, a cooler core 12 and a blower or the like is storable inside, and then a closed cross section of this structural body 3 is made to be larger, enhancing its rigidity strong enough, and this rigidity against various kinds of inputting is kept up without using any reinforce such as a deck cross-member or the like, whereby this rigidity sufficient enough against various input operations is secured without increasing weight and cost.