A high-strength steel sheet for warm working, having a tensile strength of 1180 MPa or more and a Vickers hardness, after warm working has been performed, of 400 or more, wherein the tensile strength is measured in accordance with the section in the description entitled "Tensile test at room temperature" and the Vickers hardness is measured in accordance with the section in the description entitled "Vickers hardness test at room temperature after warm working has been performed", further having a chemical composition containing, by mass%, C: 0.05% to 0.20%, Si: 3.0% or less, Mn: 3.5% to 8.0%, P: 0.100% or less, S: 0.02% or less, Al: 0.01% to 3.0%, N: 0.010% or less, one or more selected from Nb: 0.005% to 0.20%, Ti: 0.005% to 0.20%, Mo: 0.005% to 1.0%, V: 0.005% to 1.0%, optionally one or more selected from Cr: 0.005% to 2.0%, Ni: 0.005% to 2.0%, Cu: 0.005% to 2.0%, B: 0.0001% to 0.0050%, Ca: 0.0001% to 0.0050%, REM: 0.0001% to 0.0050%, Sn: 0.01% to 0.50%, and Sb: 0.0010% to 0.10%, optionally Zr, Mg, La, and Ce in a total amount of 0.002% or less, and the balance being Fe and inevitable impurities and a steel sheet microstructure including only, in terms of area ratio, 10% to 60% of retained austenite, 10% to 80% of ferrite, 10% to 50% of martensite, and 0% to 5% of bainite, wherein a C content in the retained austenite is less than 0.40 mass%, wherein the C content in retained austenite is calculated by using equation : a = 0.3578 + 0.0033 C + 0.000095 Mn + 0.00006 Cr + 0.0022 N + 0.00056 Al + 0.00015 Cu + 0.00031 Mo where [C] denotes the content in mass% of C in retained austenite, where [Mn], [Cr], [N], [Al], [Cu] and [Mo] denote the respective contents of Mn, Cr, N, Al, Cu and Mo in the whole steel and where a denotes the lattice constant (nm) of retained austenite, calculated by using equation : a = 0.17889 ⋅ 2 0.5 / sin θ where a denotes the lattice constant in nm of retained austenite and θ denotes a value calculated by dividing the diffraction peak angle in rad of the -plane by 2, wherein an average crystal grain diameter of each of the retained austenite, the martensite, and the ferrite is 2.0 μm or less, and carbides containing at least one selected from Nb, Ti, Mo, and V are present at grain boundaries. C: 0.05% to 0.20%, Si: 3.0% or less, Mn: 3.5% to 8.0%, P: 0.100% or less, S: 0.02% or less, Al: 0.01% to 3.0%, N: 0.010% or less, one or more selected from Nb: 0.005% to 0.20%, Ti: 0.005% to 0.20%, Mo: 0.005% to 1.0%, V: 0.005% to 1.0%, optionally one or more selected from Cr: 0.005% to 2.0%, Ni: 0.005% to 2.0%, Cu: 0.005% to 2.0%, B: 0.0001% to 0.0050%, Ca: 0.0001% to 0.0050%, REM: 0.0001% to 0.0050%, Sn: 0.01% to 0.50%, and Sb: 0.0010% to 0.10%, optionally Zr, Mg, La, and Ce in a total amount of 0.002% or less, and the balance being Fe and inevitable impurities and a steel sheet microstructure including only, in terms of area ratio, 10% to 60% of retained austenite, 10% to 80% of ferrite, 10% to 50% of martensite, and 0% to 5% of bainite, wherein a C content in the retained austenite is less than 0.40 mass%, wherein the C content in retained austenite is calculated by using equation : a = 0.3578 + 0.0033 C + 0.000095 Mn + 0.00006 Cr + 0.0022 N + 0.00056 Al + 0.00015 Cu + 0.00031 Mo where [C] denotes the content in mass% of C in retained austenite, where [Mn], [Cr], [N], [Al], [Cu] and [Mo] denote the respective contents of Mn, Cr, N, Al, Cu and Mo in the whole steel and where a denotes the lattice constant (nm) of retained austenite, calculated by using equation : a = 0.17889 ⋅ 2 0.5 / sin θ where a denotes the lattice constant in nm of retained austenite and θ denotes a value calculated by dividing the diffraction peak angle in rad of the -plane by 2, wherein an average crystal grain diameter of each of the retained austenite, the martensite, and the ferrite is 2.0 μm or less, and carbides containing at least one selected from Nb, Ti, Mo, and V are present at grain boundaries. <EOS>