Hybrid mold steel and manufacturing method thereof

Provided is a mold steel for plastic injection that is excellent in fatigue strength and tensile strength and available for long term use, where the mold steel includes: 0.15 to 0.40 wt% of carbon (C), 0.15 to 0.50 wt% of silicon (Si), 0.70 to 1.50 wt% of manganese (Mn), 0.50 to 1.20 wt% of nickel (Ni), 1.50 to 2.50 wt% of chrome (Cr), 0.25 to 0.70 wt% of molybdenum (Mo), 0.20 wt% or less of vanadium (V), 0.010 wt% or less of boron (B), and a trace of iron (Fe) and a plurality of impurities. Because of fatigue strength excellence and tensile strength excellence, the mold steel is available in long-term use, thereby being environment friendly; eliminates the need for additional manufacture of molds, thereby reducing the cost for additional manufacture of molds; and facilitates the large-scaled injection-based production of plastics.