In the present specification, disclosed is a high-strength welded joint having improved high-heat-input toughness by controlling a microstructure. The high-strength welded joint having improved high-heat-input toughness, according to an embodiment of the present disclosure, may include, in percent by weight (wt%), at least 0.03% but not more than 0.045% of C, at least 1.45% but not more than 1.55% of Mn, at least 0.3% but not more than 0.4% of Si, at least 0.02% but not more than 0.03% of Al, at least 1.55% but not more than 1.70% of Ni, at least 0.05% but not more than 0.07% of Cr, at least 0.05% but not more than 0.08% of Cu, at least 0.14% but not more than 0.2% of Mo, at least 0.06% but not more than 0.07% of Ti, at least 0.004% but not more than 0.005% of Nb, at least 0.035% but not more than 0.05% of O, at least 40 ppm but not more than 180 ppm of N, more than 0 ppm but not more than 80 ppm of P, more than 0 ppm but not more than 90 ppm of S, and the balance being iron (Fe) and other inevitable impurities.