A steel component (100; 400) that is made of starting material steel comprising, as chemical components: C (carbon): 0.05 mass% or more to 0.30 mass% or less; Si (silicon): 1.0 mass% or more to 3.0 mass% or less; Mn (manganese): 0.1 mass% or more to 3.0 mass% or less; P (phosphorus): 0.03 mass% or less; S (sulfur): 0.001 mass% or more to 0.150 mass% or less; Cr (chromium): 0.01 mass% or more to 0.20 mass% or less; Al (aluminum): 0.01 mass% or more to 0.05 mass% or less; N (nitrogen): 0.003 mass% or more to 0.030 mass% or less; optionally one or two of Mo (molybdenum): 0.01 mass% or more to 0.50 mass% or less, and B (boron): 0.0005 mass% or more to 0.0050 mass% or less; optionally one or two of Nb (niobium): 0.01 mass% or more to 0.30 mass% or less, Ti (titanium): 0.005 mass% or more to 0.200 mass% or less, and V (vanadium): 0.01 mass% or more to 0.20 mass% or less; and Fe and unavoidable impurities: a balance, wherein a concentration of C in a surface layer (31; 431) of the steel component (100; 400) is higher than a concentration of C in the starting material steel, wherein the surface layer (31; 431) is a region at depths from 20 μm or more and 40 μm or less from an outer circumferential surface of the steel component (100; 400) in a perpendicular direction to the outer circumferential surface, characterized in that the concentration of C in the surface layer (31; 431) of the steel component (100; 400) is 0.85 mass% or more to 1.2 mass% or less, the surface layer (31; 431) has a volume ratio of a retained-austenite structure of higher than 0% and lower than 10%, a remainder of the surface layer is a martensitic structure, and an area fraction of grain boundary carbides in the surface layer is lower than 2%, and a layer (32; 432) inside the surface layer (31; 431) has a volume ratio of a retained-austenite structure higher than the volume ratio of the retained-austenite structure in the surface layer (31; 431), and in the layer (32; 432) inside the surface layer (31; 431), a remainder is a martensitic structure. C (carbon): 0.05 mass% or more to 0.30 mass% or less; Si (silicon): 1.0 mass% or more to 3.0 mass% or less; Mn (manganese): 0.1 mass% or more to 3.0 mass% or less; P (phosphorus): 0.03 mass% or less; S (sulfur): 0.001 mass% or more to 0.150 mass% or less; Cr (chromium): 0.01 mass% or more to 0.20 mass% or less; Al (aluminum): 0.01 mass% or more to 0.05 mass% or less; N (nitrogen): 0.003 mass% or more to 0.030 mass% or less; optionally one or two of Mo (molybdenum): 0.01 mass% or more to 0.50 mass% or less, and B (boron): 0.0005 mass% or more to 0.0050 mass% or less; optionally one or two of Nb (niobium): 0.01 mass% or more to 0.30 mass% or less, Ti (titanium): 0.005 mass% or more to 0.200 mass% or less, and V (vanadium): 0.01 mass% or more to 0.20 mass% or less; and Fe and unavoidable impurities: a balance, wherein a concentration of C in a surface layer (31; 431) of the steel component (100; 400) is higher than a concentration of C in the starting material steel, wherein the surface layer (31; 431) is a region at depths from 20 μm or more and 40 μm or less from an outer circumferential surface of the steel component (100; 400) in a perpendicular direction to the outer circumferential surface, characterized in that the concentration of C in the surface layer (31; 431) of the steel component (100; 400) is 0.85 mass% or more to 1.2 mass% or less, the surface layer (31; 431) has a volume ratio of a retained-austenite structure of higher than 0% and lower than 10%, a remainder of the surface layer is a martensitic structure, and an area fraction of grain boundary carbides in the surface layer is lower than 2%, and a layer (32; 432) inside the surface layer (31; 431) has a volume ratio of a retained-austenite structure higher than the volume ratio of the retained-austenite structure in the surface layer (31; 431), and in the layer (32; 432) inside the surface layer (31; 431), a remainder is a martensitic structure.