Head-protecting airbag device

A door portion, provided at the lower periphery of an airbag cover, is pushed open by an inflating airbag (34). The airbag cover has portions split in a front and rear directions. A split portion (20A,20B,20C) located foremost covering the interior side of a front pillar, is extensively disposed upward to an area rearward of the intersection of front pillar and a roof side rail.