In an automobile seat, a portion of a side airbag is disposed further toward a vehicle front side than an inflator. Therefore, the side airbag can be expanded toward a vehicle front side of an outer-side side support portion, i.e., toward a side of a waist portion of a passenger. Moreover, because the inflator is disposed at a vehicle front side of an outer-side side frame, the inflator can be set close to a center of a waist of a passenger for which restraining by the side airbag is desired. Further, because the side airbag and the inflator are not structures that are disposed so as to interpose the outer-side side frame 20B therebetween, ease of assembly into a seatback is good.