PURPOSE: To obtain a steel for an oil well having excellent resistance to carbon dioxide corrosion and sulfide stress corrosion cracking by subjecting a specifically composed high Cr steel contg. Ni, Cu and Mo in limited amt. to a heat treatment at the limited heating temp. in the stage of hardening.

CONSTITUTION: A steel contg., by weight, 0.16W0.22% C, ≤0.8% Si, 0.25W1.00% Mn, 12.0W13.5% Cr, ≤0.10% Al, ≤0.10% Ni, ≤0.10% Cu and ≤0.05% Mo, contg., if necessary, ≥1 kind of 0.020W0.045% Nb and 0.01W0.08% V, consisting of the balance Fe with inevitable impurities, and contg. ≤0.025% P and ≤0.010% S in the impurities is heated to 920W1,050°C and thereafter the steel is hardened from said temp. region and is in succession tempered at ≥625°C and the Ac1 point or below.