A pillar trim on the vehicle-interior side of a pillar includes a pillar trim body located below an airbag and connected at its upper end part to the lower end of a top sealing member. A plurality of guide platforms are raised from the upper end part of the pillar trim body at spaced intervals in the vehicle front-to-rear direction to guide the inflation of the airbag towards the vehicle interior. The basal ends of each adjacent guide platforms are joined by a connecting part between the adjacent guide platforms. A groove for receiving the lower end of the top sealing member is formed between the vehicle-interior sides of the guide platforms and the pillar trim body. A through hole is vertically formed at least between the connecting part and the pillar trim body to open into the groove.