Seat back frame for vehicle

A seat back frame for a vehicle for supporting a seat back, comprising:

• 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;
• a cross ember arranged so as to connect the first back frame and the second back frame;
• one of a protruding portion or a recessed portion formed at the cross member so as to extend in a longitudinal direction thereof;
• one of a complementary first recessed surface portion or a first protruding surface portion formed at the first back frame so as to be complementarily connected to the protruding portion or the recessed portion of the cross member;
• one of a complementary second recessed surface portion or a second protruding surface portion formed at the second back frame so as to be connected to the protruding portion or the recessed portion of the cross member and
• wherein the first back frame is a hollow column shape, the first back frame includes a first side plate portion forming one side surface of the first back frame, a first wall portion and a second wall portion, which are formed by bending end portions of the first side plate portion so as to form a recess at a rear side of a seat, so as to be positioned at the rear side and a front side of the seat, respectively, a second side plate portion, which is obtained by bending a side end portion of the first wall portion towards the rear side of the seat so as to be substantially parallel with the first side plate portion, and a third side plate portion, which is obtained by bending a side end portion of the second wall portion towards the front side of the seat so as to be substantially parallel with the first side plate portion, the third side plate portion is overlapped on the second side plate portion so as to be in contact with each other, and the second side plate portion and the third side plate portion are connected at an overlapped portion in a vicinity of a bent portion between the first wail portion and the second side plate portion.