To enhance strength by means of making a frame shape flow smooth and to reduce the concentration of stress by forming a pawl where the end of the rear flap of a trim cover is hooked at the side of a forward and upward inclining part which is erected on a surface being the same as the lower surface of a flat part in a planar frame member on the lower surface.

In a seat cushion frame to be suitably used for the seat cushion of a passenger seat in an automobile, the pawl 20 is worked to be formed at the side of the forward and upward inclining part 17 which is erected on the surface being the same as the lower surface 19 of the flat part 16 in a transit part 18 which is changed from the flat part 16 into the forward and upward inclining part 17 in the planar vertical frame member 15. Then a seat cushion pad is placed on it, the trim cover is put over it and, then, a slit formed in the end of the rear flap of the trim cover is hooked at the pawl 20 so that hook-fixing is attained. Thus, the end of the trim cover is easily treated.