A spring consists of, by weight %, 0.27 to 0.48% of C, 0.01 to 2.2% of Si, 0.30 to 1.0% of Mn, not more than 0.035% of P, not more than 0.035% of S, and the balance of Fe and inevitable impurities. The spring has a nitrogen compound layer and a carbon compound layer at the surface at a total thickness of not more than 2 μm. The spring has a center portion with hardness of 500 to 700 HV in a cross section and has a compressive residual stress layer at a surface layer. The compressive residual stress layer has a thickness of 0.30 mm to D/4, in which D (mm) is a circle-equivalent diameter of the cross section, and has maximum compressive residual stress of 1400 to 2000 MPa.