To prevent the closure of a passage for scavenging a blowby gas, due to freezing.

This ram air adjusting device includes an opening and closing mechanism 10 capable of variably controlling the opening of a front grille as an air intake port, for adjusting the amount of air to be taken into an engine room 11 storing an internal combustion engine 0, and a control part for correcting the opening of the opening and closing mechanism 10 to be smaller as the amount of blowby gas generated in the internal combustion engine 0 is smaller when an air temperature is a predetermined one or lower.