VEHICLE SEAT BACK FRAME

In a back frame applied to a seatback, a first flange of a first reinforcing member is joined to a panel member at either or both of a portion on at least either of sides across a diagonal center line of the panel member and a portion crossing the diagonal center line, and second flanges of the first reinforcing member are joined to the panel member at respective portions on one side and the other side across the diagonal center line. A part of a second reinforcing member on a side of an intersection point between a first side part and a second side part of the panel member is overlapped and joined with a first wall of the first reinforcing member.