The invention provides a steel and a steel pipe for high-strength pipe lines for sour gas service that have excellent anti-HIC property capable of satisfying the severe requirement for anti-HIC property necessary for line pipes for sour gas service having a pipe thickness of at least 20 mm. Concretely, the steel contains, in terms of % by weight, C: 0.02 to 0.06%, Si: 0.5% or less, Mn: 0.8 to 1.6%, P: 0.008% or less, S: 0.0008% or less, Al: 0.08% or less, Nb: 0.005 to 0.035%, Ti: 0.005 to 0.025%, and Ca: 0.0005 to 0.0035%, and optionally contains one or more of Cu: 0.5% or less, Ni: 1% or less, Cr: 0.5% or less, Mo: 0.5% or less and V: 0.1% or less, and has a CP value of 0.95 or less represented by CP = 4.46C(%) + 2.37Mn(%)/6 + {1.18Cr(%) + 1.95Mo(%) + 1.74V(%)}/5 + {1.74Cu(%) + 1.7Ni(%)}/15+22.36P(%), and a Ceq value of 0.30 or more represented by Ceq = C(%) + Mn(%)/6 + {Cr(%) + Mo(%) + V(%)}/5 + {Cu(%) + Ni(%)}/15.