A head protecting airbag device of the invention is provided with an airbag which expands to cover the vehicular interior sides of a window and a pillar garnish. Near the front or rear edge of an inner panel, a guide member is so arranged in the vertical direction that its vehicular interior side is covered by the edge portion of the pillar garnish. A flexible connection member, which is slidably connected to the guide member, is connected to a portion of the airbag toward the center of the window. Moreover, the connection member pushes open the edge portion of the pillar garnish toward the vehicular interior side as the connection member slides downward along the guide member when the airbag expands.