Abstract: In a vehicle seat, a back side, that is a side opposite a seating side, of a cushion is covered by a backing that has less expandability than the cushion. The back side of the cushion is divided by a pair of first supporting members into a center portion arranged between the pair of first supporting members and a pair of side portions arranged on both sides of the center portion. The center portion and the side portions each have a semi-cylindrical outer shape that protrudes out from the back side of the cushion. First arranging portions that are recessed toward the seating side are formed between the center portion and each of the side portions. The first supporting members are arranged sinking into the cushion at the first arranging portions.