A seat back frame for a vehicle for supporting a seat back, includes a first back frame, at which a shoulder belt anchor for supporting one end portion of a seat belt is provided, a second back frame arranged substantially in parallel with the first back frame, and a cross member connecting the first back frame and the second back frame, wherein a protruding portion or a recessed portion is formed at the cross member so as to extend in a longitudinal direction thereof, a first recessed surface portion or a first protruding surface portion is formed at the first back frame and a second recessed surface portion or a second protruding surface portion is formed at the second back frame so that the first back frame and the second back frame are fittedly connected to the protruding portion or the recessed portion of the cross member.