A high-strength steel sheet according to the present invention not only is suitably adjusted in its chemical elements composition, but also has a DE value defined by the following Equation (1) of 0.0340% or more, and a carbon equivalent Ceq defined by the following Equation (2) of 0.45% or less:DE value=[Ti]+[Nb]+0.3[V]+0.0075[Cr] (1)where, [Ti], [Nb], [V], and [Cr] represent contents (mass %) of Ti, Nb, V, and Cr, respectively;Ceq=[C]+[Mn] / 6+([Cr]+[Mo]+[V]) / 5+([Cu]+[Ni]) / 15 (2)where, [C], [Mn], [Cr], [Mo], [V], [Cu], and [Ni] represent contents (mass %) of C, Mn, Cr, Mo, V, Cu, and Ni, respectively. A high-strength steel sheet resistant to strength reduction and good in low-temperature toughness of HAZ even when subjected for a long time to a stress-relief annealing process after being processed by welding, is provided.