A hot-work mold steel includes 0.37 to 0.46 wt % of carbon (C), 0.25 to 0.5 wt % of silicon (Si), 0.36 to 0.56 wt % of manganese (Mn), 2.0 to 5.0 wt % of chromium (Cr), 1.4 to 2.6 wt % of molybdenum (Mo), 0.4 to 0.8 wt % of vanadium (V), 0.0007 to 0.004 wt % of boron (B), 0.002 to 0.022 wt % of aluminum (Al), 0.001 to 0.09 wt % of titanium (Ti) and the remainder of iron (Fe) and inevitable impurities. The hot-work mold steel exhibits superior thermal conductivity, hardenability, durability, and nitriding characteristics, and increased resistance to heat check and melt-out. A die-casting mold made of the steel has improved thermal conductivity regardless of mold size and a prolonged life cycle and can improve the surface quality in manufactured parts.