STEEL SHEET EXCELLENT IN TOUGHNESS IN WELDED JOINT AND PRODUCING PROCESS THEREOF

A steel sheet which increases toughness of a matrix itself, prevents coarsening of grains particularly in a heat-affected zone more certainly, and has excellent toughness in the heat-affected zone by forming complex precipitates of Ti nitride and Nb carbonitride in a steel material in the finely dispersed state, and a method for producing the same are provided. A steel sheet having excellent toughness in a welded joint contains, by mass percent, 0.02 to 0.12% of C, 0.002 to 0.010% of N, 0.005 to 0.025% of Ti, and 0.003 to 0.025% of Nb, wherein complex precipitates of Ti nitride and Nb carbonitride present within a cross-sectional area of the steel sheet in a number of 100 precipitates/mm^2 of the cross-sectional area. The steel sheet additionally satisfies 0.5 to 1.8% of Mn, 0.7% or less of Si, and 0.1% or less of Al. The steel sheet additionally contains at least one of 0.0005 to 0.005% of B and 0.01 to 0.5% of Ni. The steel sheet additionally contains at least one selected from the group consisting of 0.0003 to 0.05% of Zr, 0.0005 to 0.005% of Ca, 0.0005 to 0.005% of Mg, and 0.0005 to 0.01% of REM. The steel sheet additionally contains at least one selected from the group consisting of 0.01 to 0.5% of Cu, 0.05 to 0.5% of Cr, 0.01 to 0.5% of Mo, and 0.005 to 0.1% of V.