PURPOSE: To obtain a steel for hot forging die improving the service life of die at relatively low temp., by limiting respective quantities of C, Si, Mn, P, S, Cr, Mo, V, and Al and also by controlling Ni content in correlation with the surface temp. of a die in the course of hot forging.

CONSTITUTION: The steel for hot forging die is composed of an alloy steel which has a composition consisting of, by weight, 0.50W0.70% C, ≤0.50% Si, 0.20W0.90% Mn, ≤0.035% P, ≤0.015% S, 0.50W2.0% Cr, 0.20W0.60% Mo, 0.04W0.30% V, ≤0.10% acid-soluble Al, and the balance Fe with inevitable impurities and further containing Ni so that -0.025T+19≤Ni≤-0.025T+21 (where T means the surface temp. of a die in the course of hot forging, °C) is satisfied. This steel has superior wear resistance and toughness in use under the condition of <about 750°C die-surface temp. and it is excellent in cracking resistance as well.