An automotive frame part that is an A-pillar-lower part, the A-pillar-lower part including: an outer panel having approximately a T-shape in planar view and a cross section intersecting a portion corresponding to a horizontal side and a vertical side of the T-shape is a hat-shaped cross section including a top portion, a side wall portion, and a flange portion; an inner panel being connected to the flange portion and forming a closed cross section with the outer panel; and plastic stiffening members that each have one end connected to an inner surface of the outer panel and another end connected to an inner surface of the inner panel, wherein the shape and the disposition of the stiffening members are set based on an analysis result from a shape optimization analysis method and each of the stiffening members has a columnar shape or a columnar shape with both end parts bulging.