Abstract: A non-heat treated steel for a crankshaft of the present invention comprises iron (Fe) as a main component and also comprises 0.37 to 0.43 mass % of carbon (C), 0.15 to 0.35 mass % of silicon (Si), 0.90 to 1.30 mass % of manganese (Mn), 0.08 to 0.15 mass % of vanadium (V); and the content of phosphorous (P) is 0.030 mass % or less, the content of copper (Cu) is 0.300 mass % or less, the content of nickel (Ni) is 0.30 mass % or less, and the content of chromium (Cr) is 0.35 mass % or less. The non-heat treated steel also comprises 0.010 to 0.035 mass % of sulfur (S) and 0.02 to 0.05 mass % of bismuth (Bi), which are machinability-improving elements. Thus, the non-heat treated steel has a high fatigue strength and a high yield strength and also has an excellent machinability.