An acoustic structure of seat back includes a suspension board element provided therein. The suspension board element, which has a speaker unit provided to a backward surface thereof, is resiliently provided in a seat back frame of the seat back. A sound-conductive cushion element of a flat plate configuration is juxtaposed on a forward surface of the suspension board element. Those seat back frame and sound-conductive cushion element are covered with a foam padding and a trim cover assembly to thereby form such an acoustic seat back structure wherein all the suspension board element, speaker unit and sound-conductive cushion element are resiliently supported within the seat back, as an acoustic and vibration generator unit effective for imparting sound and vibration directly to a back portion of seat occupant.