A seat apparatus includes: a seat cushion provided in a vehicle; a seat back pivotably joined to the seat cushion, the seat back capable of being folded forward so as to be superposed on the seat cushion; a seat storage unit in which the seat cushion and the seat back are stored in a folded state; and a headrest attached to the seat back via a pivotable member, the headrest capable of being stored in a clearance defined between a back supporting surface of the seat back and a sitting surface of the seat cushion when the seat cushion and the seat back are folded.