Junction regions are formed by mutually joined side portions of a pillar inner and a pillar outer, and an opening-defining region is formed by mutually spaced side portions of the pillar inner and the pillar outer. The junction regions include a first junction region adjacent to the opening-defining region on one side in a longitudinal direction and a second junction region adjacent to the opening-defining region on the other side in the longitudinal direction. A bypass connection wall connecting the opening-defining region and at least one of the first junction region and the second junction region extends from at least one of the pillar inner and the pillar outer.