The knee-protecting airbag apparatus includes an airbag folded and housed in a lower area inside the column cover. The airbag pushes and opens a door section on the column cover upon deployment. When the door section is thus opened, a door of the door section blocks off an allowance gap formed between an outer circumference of the column cover subjected to position adjustment and a lower area of a peripheral region of an installation opening on a dashboard for installing the column cover by locating a rear edge region of the door to abut on a rear side of the dashboard or the lower area of the peripheral region of the installation opening on the rear side of the dashboard.