A vehicular pedestrian protecting airbag device that is capable of suppressing increases in weight and cost accompanying reinforcement measures, and capable of maintaining good pedestrian protection performance of an upper face of a hood. An automobile pedestrian protecting airbag device is installed at a vehicle lower side of a rear end section of a hood at a vehicle rear side of a protruded portion. A pedestrian protecting airbag and an inflator are installed inside a module case. The inflator is attached to a bottom wall of the protruded portion by inflator attachment brackets each formed with an excess length portion at an intermediate portion. Accordingly, when the inflators attempt to move toward the vehicle front side due to deployment reaction force of the pedestrian protecting airbag, the excess length portions are compressed and deform to enable the deployment reaction force to escape.