Seat back frame structure of seat for vehicle and seat for vehicle with seat back frame structure

An object of the present invention is to provide a seat back frame structure for a vehicle and a seat for a vehicle with such a seat back frame structure which are capable of securing a necessary strength or rigidity, while at the same time attaining the decrease of its weight and its cost. There is provided a seat back frame structure of a seat for a vehicle comprising a seat back frame structure a lower end of which is connected to a rear end of a seat cushion frame structure in such a way that the seat back frame structure can be inclined relative to the seat cushion frame structure, said seat back frame structure includes a pair of side frames each of which extends in a vertical direction of the vehicle, and an oblique wire on at least one of said pair of side frames an upper end of which is fixed to a side portion of said at least one of the pair of side frames and a lower end of which is fixed to said seat back frame structure at a position forward of a rotational center of said seat back frame structure, said oblique wire includes a characteristics in such a way that, in a case where a load toward a rear side of the vehicle is loaded on said seat back frame structure, it has a tension force exert on said seat back frame structure so as to alleviate a moment acting on said seat back frame structure caused by said load, while it does not resist a compressive force from outside thereof.