A welding structural steel product exhibiting a superior heat affected zone toughness, comprising, in terms of percent by weight, 0.03 to 0.17% C, 0.01 to 0.5% Si, 0.4 to 2.0% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.008 to 0.030% N, 0.0003 to 0.01% B, 0.001 to 0.2% W, at most 0.03% P, at most 0.03% S, at most 0.005% O, and balance Fe and incidental impurities while satisfying conditions of 1.2.ltoreq.Ti/N.ltoreq.2.5, 10.ltoreq.N/B.ltoreq.40, 2.5.ltoreq.Al/N.ltoreq.7, and 6.5.ltoreq.(Ti+2Al+4B)/N.ltoreq.14, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 .mu.m or less. The method includes the steps of preparing a slab of the above-described composition, heating the slab to 1,100.degree. C. to 1,250.degree. C. for 60-180 minutes, hot rolling the heated slab in an austenite recrystallization range at a 40% or more rolling reduction followed by controlled cooling.