Abstract: The alloy steel consists (by weight) of C 0.8-1.2%, Si 1.0-2.5%, Mn 0.2-1.0%, Cr 15.0-25.0%, one or both Ni 0.5-3.5% and Co 0.3-5.0%, where both Ni and Co are used, the sum of Ni and Co being 1.0-5.0%, one or both of Mo 0.3-3.5% and W 0.5-3.5%, when both Mo and W are used, the sum of Mo and W being 0.5-3.5% and the balance of Fe and inpurities. Where one, two or more of less than 0.5% of Al, less than 1.0% of Cu, less than 0.5% of V, less than 1.0% of Nb, less than 0.3% Ti, less than 0.25% of Zr, less than 0.2% of B and less than 0.3% of N are contained, the wear resistant and heat resistant property of the alloy can be improved further.