Abstract: There is provided a seat back frame in which the same frame can be used for both of single reclining and double reclining, and the deformation of side frame can be controlled against a backward load. The seat back frame is composed of bilaterally symmetrical side frames, an upper pipe welded to both upper end portions of the side frames, and a lower pipe welded to the lower portions of the side frames. The side frames have a wider-in-front shape such that the width is greater on the front side than on the rear side. On the face of the side frame, triangular planes are provided so as to be vertically adjacent to each other, and the common side of the adjacent triangles is bent.

Abstract: There is provided a seat back frame in which the same frame can be used for both of single reclining and double reclining, and the deformation of side frame can be controlled against a backward load. The seat back frame is composed of bilaterally symmetrical side frames, an upper pipe welded to both upper end portions of the side frames, and a lower pipe welded to the lower portions of the side frames. The side frames have a wider-in-front shape such that the width is greater on the front side than on the rear side. On the face of the side frame, triangular planes are provided so as to be vertically adjacent to each other, and the common side of the adjacent triangles is bent.