Spring steel comprising: a chemical composition consisting of, C: greater than 0.35 mass % and less than 0.50 mass %, Si: greater than 1.75 mass % and equal to or less than 3.00 mass %, Mn: 0.2 mass % to 1.0 mass % (inclusive of 0.2 mass % and 1.0 mass %), Cr: 0.01 mass % to 0.04 mass % (inclusive of 0.01 mass % and 0.04 mass %), P: 0.025 mass % or less, S: 0.025 mass % or less, Mo: 0.1 mass % to 1.0 mass % (inclusive of 0.1 mass % and 1.0 mass %), O: 0.0015 mass % or less; and optionally further at least one element selected from: N: 0.005 mass % to 0.020 mass % (inclusive of 0.005 mass % and 0.020 mass %), A1: 0.01 mass % to 0.50 mass % (inclusive of 0.01 mass % and 0.50 mass %); Cu: 0.005 mass % to 1.0 mass % (inclusive of 0.005 mass % and 1.0 mass %); Ni: 0.005 mass % to 2.0 mass % (inclusive of 0.005 mass % and 2.0 mass %), W: 0.001 mass % to 2.0 mass % (inclusive of 0.001 mass % and 2.0 mass %); Nb: 0.001 mass % to 0.1 mass % (inclusive of 0.001 mass % and 0.1 mass %); Ti: 0.001 mass % to 0.2 mass % (inclusive of 0.001 mass % and 0.2 mass %); V: 0.002 mass % to 0.5 mass % (inclusive of 0.002 mass % and 0.5 mass %), further containing: B: 0.0002 mass % to 0.005 mass % (inclusive of 0.0002 mass % and 0.005 mass %); and the balance as incidental impurities and Fe; and microstructure with martensite fraction of 90% or more, wherein a PC value calculated by Formula below is greater than 3.3 and equal to or less than 8.0, and the spring steel has tensile strength of 1900 MPa or more, PC = 4.2 × C + Mn × 0.1 × 1 / Si + 1 / Mo + 20.3 × Cr + 0.001 × 1 / N wherein the chemical composition further satisfies Formula below: Cr / Mo ≤ 0.35 and wherein [brackets] denote the content of an element in the brackets (in mass %). a chemical composition consisting of, C: greater than 0.35 mass % and less than 0.50 mass %, Si: greater than 1.75 mass % and equal to or less than 3.00 mass %, Mn: 0.2 mass % to 1.0 mass % (inclusive of 0.2 mass % and 1.0 mass %), Cr: 0.01 mass % to 0.04 mass % (inclusive of 0.01 mass % and 0.04 mass %), P: 0.025 mass % or less, S: 0.025 mass % or less, Mo: 0.1 mass % to 1.0 mass % (inclusive of 0.1 mass % and 1.0 mass %), O: 0.0015 mass % or less; and optionally further at least one element selected from: N: 0.005 mass % to 0.020 mass % (inclusive of 0.005 mass % and 0.020 mass %), A1: 0.01 mass % to 0.50 mass % (inclusive of 0.01 mass % and 0.50 mass %); Cu: 0.005 mass % to 1.0 mass % (inclusive of 0.005 mass % and 1.0 mass %); Ni: 0.005 mass % to 2.0 mass % (inclusive of 0.005 mass % and 2.0 mass %), W: 0.001 mass % to 2.0 mass % (inclusive of 0.001 mass % and 2.0 mass %); Nb: 0.001 mass % to 0.1 mass % (inclusive of 0.001 mass % and 0.1 mass %); Ti: 0.001 mass % to 0.2 mass % (inclusive of 0.001 mass % and 0.2 mass %); V: 0.002 mass % to 0.5 mass % (inclusive of 0.002 mass % and 0.5 mass %), further containing: B: 0.0002 mass % to 0.005 mass % (inclusive of 0.0002 mass % and 0.005 mass %); and the balance as incidental impurities and Fe; and microstructure with martensite fraction of 90% or more, C: greater than 0.35 mass % and less than 0.50 mass %, Si: greater than 1.75 mass % and equal to or less than 3.00 mass %, Mn: 0.2 mass % to 1.0 mass % (inclusive of 0.2 mass % and 1.0 mass %), Cr: 0.01 mass % to 0.04 mass % (inclusive of 0.01 mass % and 0.04 mass %), P: 0.025 mass % or less, S: 0.025 mass % or less, Mo: 0.1 mass % to 1.0 mass % (inclusive of 0.1 mass % and 1.0 mass %), O: 0.0015 mass % or less; and optionally further at least one element selected from: N: 0.005 mass % to 0.020 mass % (inclusive of 0.005 mass % and 0.020 mass %), A1: 0.01 mass % to 0.50 mass % (inclusive of 0.01 mass % and 0.50 mass %); Cu: 0.005 mass % to 1.0 mass % (inclusive of 0.005 mass % and 1.0 mass %); Ni: 0.005 mass % to 2.0 mass % (inclusive of 0.005 mass % and 2.0 mass %), W: 0.001 mass % to 2.0 mass % (inclusive of 0.001 mass % and 2.0 mass %); Nb: 0.001 mass % to 0.1 mass % (inclusive of 0.001 mass % and 0.1 mass %); Ti: 0.001 mass % to 0.2 mass % (inclusive of 0.001 mass % and 0.2 mass %); V: 0.002 mass % to 0.5 mass % (inclusive of 0.002 mass % and 0.5 mass %), further containing: B: 0.0002 mass % to 0.005 mass % (inclusive of 0.0002 mass % and 0.005 mass %); and the balance as incidental impurities and Fe; and N: 0.005 mass % to 0.020 mass % (inclusive of 0.005 mass % and 0.020 mass %), A1: 0.01 mass % to 0.50 mass % (inclusive of 0.01 mass % and 0.50 mass %); Cu: 0.005 mass % to 1.0 mass % (inclusive of 0.005 mass % and 1.0 mass %); Ni: 0.005 mass % to 2.0 mass % (inclusive of 0.005 mass % and 2.0 mass %), W: 0.001 mass % to 2.0 mass % (inclusive of 0.001 mass % and 2.0 mass %); Nb: 0.001 mass % to 0.1 mass % (inclusive of 0.001 mass % and 0.1 mass %); Ti: 0.001 mass % to 0.2 mass % (inclusive of 0.001 mass % and 0.2 mass %); V: 0.002 mass % to 0.5 mass % (inclusive of 0.002 mass % and 0.5 mass %), further containing: B: 0.0002 mass % to 0.005 mass % (inclusive of 0.0002 mass % and 0.005 mass %); and the balance as incidental impurities and Fe; and microstructure with martensite fraction of 90% or more, wherein a PC value calculated by Formula below is greater than 3.3 and equal to or less than 8.0, and the spring steel has tensile strength of 1900 MPa or more, PC = 4.2 × C + Mn × 0.1 × 1 / Si + 1 / Mo + 20.3 × Cr + 0.001 × 1 / N wherein the chemical composition further satisfies Formula below: Cr / Mo ≤ 0.35 and wherein [brackets] denote the content of an element in the brackets (in mass %).