A seat back configured to support a back of a seated person includes a back frame that constitutes an internal framework; and an elastic mat that is fitted to the back frame so as to cover the back frame from a front side, the elastic mat having a planar shape and being configured to elastically support the back of the seated person. The back frame includes a frame body and a support wire that protrudes forward from the frame body. The elastic mat includes a plurality of hooks provided on a back surface of a main support portion configured to support the back of the seated person, the hooks being engaged with the support wire to fix the elastic mat to the support wire.