A vehicle seat includes a projected member that is accommodated in a seat back, and that is projected and deployed above the seat back when inflated by a gas supply; a lateral deployment member whose upper end side is connected to the projected member, whose lower end side is connected to a front end side of a seat cushion, and that is accommodated in a lateral side of the seat cushion and a lateral side of the seat back; and a tension support member whose one end side is supported by the seat back in a portion separated from the lateral deployment member in a seat width direction and whose other end side is connected to an upper end side of the lateral deployment member or the projected member.