A seat pad includes a main portion and a bank portion. When the seat pad is disposed on a seat frame, a reverse face side of the bank portion contacts the seat frame to be supported. When the bank portion is pressed in a seat width direction, the bank portion is flexurally deformed so as to be crushed around a contact portion contacting the seat frame. A contact member is relatively movably provided on a side of the backing material that faces the seat frame, and the seat pad is disposed on the seat frame while the contact member is pressed against the seat frame. When the bank portion is pressed in the seat width direction, the backing material and the seat pad including the bank portion move in a crushing direction relatively to a portion of the contact member that contacts the seat frame.