A resin-molded component includes a thin wall portion, and a rib-like projection configured to protrude from a back surface of the thin wall portion. The rib-like projection includes a plurality of plate-like projections arranged to be spaced from one another. Each of the plurality of plate-like projections is arranged such that an angle formed between a line connecting a point on a longer side of a bottom surface thereof to a gate provided in the thin wall portion and the longer side of the bottom surface thereof is within a range from 10 degrees to 80 degrees.