Seat back

A seat back comprising:

• a frame configured to form a framework;
• a lumbar support device attachable to the frame;
• a cushion member attachable to the frame for elastically supporting a seater,
• wherein the cushion member comprises a main member positioned at the center portion in a seat width direction and a pair of side members on both sides of the main member,
• wherein the main member comprises a main pad, a main cover configured to cover the main pad, and a main support member configured to support the main pad,
• wherein:
• a plurality of curved portions, extending convexly toward the inner side of the seat width direction, are formed on the main support member;
• a plurality of projections are formed on the rear surface of the main pad, wherein the plurality of projections protrudes rearward, and wherein the plurality of projections is positioned outside of the curved portions in the seat width direction in a state where the projections are in contact with the main support member;
• and
• a plurality of slits are formed at an edge of the main cover in the seat width direction, wherein the main cover is attachable to the main support member.