An austenitic cast iron, being characterized in that: it comprises: basic elements comprising carbon, silicon (Si), chromium (Cr), nickel (Ni), manganese (Mn) and copper (Cu); and the balance comprising iron (Fe) and inevitable impurities and a trace-amount modifier element, which is effective in improving characteristic, in a trace amount; wherein the trace-amount modifier element is one or more of magnesium (Mg), rare-earth elements (R.E.), aluminum (Al), calcium (Ca), barium (Ba), bismuth (Bi), antimony (Sb), tin (Sn), titanium (Ti), zirconium (Zr), molybdenum (Mo), vanadium, tungsten, niobium (Nb), nitrogen, or zinc (Zn), wherein the inevitable impurities include phosphorus and/or sulfur; it is an austenitic cast iron being a cast iron that is structured by a base comprising an Fe alloy in which an austenite phase makes a major phase in ordinary-temperature region; wherein said basic elements, the inevitable impurities, and the trace-amount modifier element(s) fall within compositional ranges that satisfy the following conditions with the entirety of said cast iron taken as 100% by mass; hereinafter being simply expressed as "%": C: from 2.0 to 3.0%; Si: from 4.0 to 5.4%; Cr: from 0.8 to 2.0%; Mn: from 3.9 to 5.6%; Ni: from 17 to 22%; Cu: from 0.9 to 1.6% S: 0.05% or less; P: 0.059% or less; and wherein the trace-amount modifier elements are 1% or less in a total content. it comprises: basic elements comprising carbon, silicon (Si), chromium (Cr), nickel (Ni), manganese (Mn) and copper (Cu); and the balance comprising iron (Fe) and inevitable impurities and a trace-amount modifier element, which is effective in improving characteristic, in a trace amount; wherein the trace-amount modifier element is one or more of magnesium (Mg), rare-earth elements (R.E.), aluminum (Al), calcium (Ca), barium (Ba), bismuth (Bi), antimony (Sb), tin (Sn), titanium (Ti), zirconium (Zr), molybdenum (Mo), vanadium, tungsten, niobium (Nb), nitrogen, or zinc (Zn), wherein the inevitable impurities include phosphorus and/or sulfur; it is an austenitic cast iron being a cast iron that is structured by a base comprising an Fe alloy in which an austenite phase makes a major phase in ordinary-temperature region; wherein said basic elements, the inevitable impurities, and the trace-amount modifier element(s) fall within compositional ranges that satisfy the following conditions with the entirety of said cast iron taken as 100% by mass; hereinafter being simply expressed as "%": C: from 2.0 to 3.0%; Si: from 4.0 to 5.4%; Cr: from 0.8 to 2.0%; Mn: from 3.9 to 5.6%; Ni: from 17 to 22%; Cu: from 0.9 to 1.6% S: 0.05% or less; P: 0.059% or less; and wherein the trace-amount modifier elements are 1% or less in a total content. basic elements comprising carbon, silicon (Si), chromium (Cr), nickel (Ni), manganese (Mn) and copper (Cu); and the balance comprising iron (Fe) and inevitable impurities and a trace-amount modifier element, which is effective in improving characteristic, in a trace amount; wherein the trace-amount modifier element is one or more of magnesium (Mg), rare-earth elements (R.E.), aluminum (Al), calcium (Ca), barium (Ba), bismuth (Bi), antimony (Sb), tin (Sn), titanium (Ti), zirconium (Zr), molybdenum (Mo), vanadium, tungsten, niobium (Nb), nitrogen, or zinc (Zn), wherein the inevitable impurities include phosphorus and/or sulfur; it is an austenitic cast iron being a cast iron that is structured by a base comprising an Fe alloy in which an austenite phase makes a major phase in ordinary-temperature region; wherein said basic elements, the inevitable impurities, and the trace-amount modifier element(s) fall within compositional ranges that satisfy the following conditions with the entirety of said cast iron taken as 100% by mass; hereinafter being simply expressed as "%": C: from 2.0 to 3.0%; Si: from 4.0 to 5.4%; Cr: from 0.8 to 2.0%; Mn: from 3.9 to 5.6%; Ni: from 17 to 22%; Cu: from 0.9 to 1.6% S: 0.05% or less; P: 0.059% or less; C: from 2.0 to 3.0%; Si: from 4.0 to 5.4%; Cr: from 0.8 to 2.0%; Mn: from 3.9 to 5.6%; Ni: from 17 to 22%; Cu: from 0.9 to 1.6% S: 0.05% or less; P: 0.059% or less;