SEATBACK FRAME AND VEHICLE SEAT

A seatback frame including left and right side frames, a lower frame, and a sacrum support section. The left and right side frames extend in a seat up-down direction inside left and right side portions of a seatback of a vehicle seat. The lower frame spans between lower end portions of the left and right side frames. The sacrum support section extends from a lower end portion of the lower frame toward a seat front side and supports a sacral region of a seated occupant from a seat rear side. A weakened portion that is weakened by a load from the seat front side is provided to the sacrum support section.