A seat back structure for a vehicle according to one aspect of the present invention including a headrest, a seat back frame, a pad disposed in front of a surface of the seat back frame, a backrest surface of the pad, and right and left side supports each provided on either side of the backrest surface in a seat width direction, in which a right slit portion and a left slit portion are provided between the backrest surface and the right and the left side supports, respectively, each of the right slit portion and the left slit portion penetrating the pad in the thickness direction of the pad and extending in a vertical direction of the pad, and the right and the left slit portions are spaced apart from each other in the seat width direction.