To provide a method for producing a steel bar showing a toughness equivalent to that of a forged one, through blooming.

In the method, the steel bar comprises a hot die steel and has a diameter of 170-250 mm. The method comprises a step for casting an ingot of a steel comprising, by mass, 0.32-0.42% C, 0.8-1.2% Si, 4.5-5.5% Cr, 1.0-1.5% Mo, 0.8-1.2% V and the balance being Fe and unavoidable impurities, a step for subjecting the obtained steel ingot to soaking treatment at a temperature below the solidus in a phase diagram of the steel but equal to or higher than solidus-100°C for (i) ≥25 hr for the steel bar with a diameter of 170-200 mm or (ii) ≥50 hr for the steel bar with a diameter of 200-250 mm, and a step for blooming the obtained treating material to be shaped into the steel bar having the target diameter.