Provided herein is an alloy steel in which carburization is prevented by a processing load, the alloy steel including: about 0.13 to 0.25 wt % of carbon (C), about 0.6 to 1.5 wt % of silicon (Si), about 0.6 to 1.5 wt % of manganese (Mn), about 1.5 to 3.0 wt % of chromium (Cr), about 0.01 to 0.1 wt % of niobium (Nb), about 0.01 to 0.1 wt % of aluminum (Al), about 0.05 to 0.5 wt % of vanadium (V), the balance iron (Fe), and impurities, based on the total weight of the alloy steel.