A steel for high-strength spring has an Ac3 transformation temperature as an indicator of the decarburization performance, which is calculated by Equation (1) below, is from 859 to 885° C., a maximum hardened diameter DI as an indicator of the hardening performance, which is calculated by Equation (2) below, is from 70 to 238 mm, and a temper hardness HRC as an indicator of the spring performance, which is calculated by Equation (3) below, is from 50 to 55. Ac3=910−203×√{square root over (C)}−15.2Ni+44.7Si+104V+31.5Mo+13.1W  (1) DI=DO×fSi×fMn×fP×fS×fCu×fNi×fCr  (2) HRC=38.99+17.48C+2.55Si−2.28Ni+2.37Cr+8.04Ti  (3) wherein, D0=8.65×√{square root over (C)}, fSi=1+0.64×% Si, fMn=1+4.10×% Mn, fP=1+2.83×% P, fS=1−0.62×% S, fCu=1+0.27×% Cu, fNi=1+0.52×% Ni, and fCr=1+2.33×% Cr.