To provide a high-performance, inexpensive low C-high Si-high Cr-B-Nb type iron-based corrosion-resistant and wear-resistant alloy that is extremely superior in corrosion resistance and wear resistance to 304 stainless steel, high-chromium cast iron and high carbon-high chromium cast-iron-type materials, has a high corrosion-resistant property that would never be obtained from a high carbon-high chromium carbide precipitation-type iron-based wear-resistant alloy and at the same time, a wear-resistant property that is superior to these metals, and further hardly causes brittle peeling that is inherent to high Si-containing steel. This alloy contains, all percentages by weight, C: 0.5 to 2.5% by weight, Si: 2.5 to 4.5%, Mn: 0 to 10% or less, Cr: 15% to 31%, Ni: 0 to 16%, Cu: 7% or less, Mo: 10% or less, B: 0.5% to 3.5%, and 0+0.083Cr+1.05 is satisfied, within a range of 27% / =570 / Cr-0.066Cr+1.145 is satisfied, and within a range of 20% / =1.25 is satisfied.