A high-strength steel sheet having a tensile strength of 1,180 MPa or more, the high-strength steel sheet having a chemical composition comprising, in percent by mass, C: 0.09% or more and 0.37% or less, Si: more than 0.70% and 2.00% or less, Mn: 2.60% or more and 3.60% or less, P: 0.001% or more and 0.100% or less, S: 0.0200% or less, Al: 0.010% or more and 1.000% or less, N: 0.0100% or less, optionally at least one selected from the group consisting of Ti: 0.001% or more and 0.100% or less, Nb: 0.001% or more and 0.100% or less, V: 0.001% or more and 0.100% or less, B: 0.0001% or more and 0.0100% or less, Mo: 0.010% or more and 0.500% or less, Cr: 0.01% or more and 1.00% or less, Cu: 0.01% or more and 1.00% or less, Ni: 0.01% or more and 0.50% or less, Sb: 0.001% or more and 0.200% or less, Sn: 0.001% or more and 0.200% or less, Ta: 0.001% or more and 0.100% or less, Ca: 0.0001% or more and 0.0200% or less, Mg: 0.0001% or more and 0.0200% or less, Zn: 0.001% or more and 0.020% or less, Co: 0.001% or more and 0.020% or less, Zr: 0.001% or more and 0.020% or less, and REM: 0.0001% or more and 0.0200% or less, with the balance being Fe and unavoidable impurities, wherein the high-strength steel sheet has a steel structure in which an area fraction of martensite having a carbon concentration of more than 0.7 × [%C] and less than 1.5 × [%C] is 55% or more; an area fraction of tempered martensite having a carbon concentration of 0.7 × [%C] or less is 5% or more and 40% or less; the ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite is 0.05 or more and 0.40 or less; and the martensite and the tempered martensite each have an average grain size of 5.3 μm or less, where [%C] represents the content in percent by mass of compositional element C in steel, wherein the area fraction of steel structures other than said martensite, tempered martensite and retained austenite is 3% or less, and wherein the tensile strength, the area fraction of martensite having a carbon concentration of more than 0.7 × [%C] and less than 1.5 × [%C], the area fraction of tempered martensite having a carbon concentration of 0.7 × [%C] or less, the ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite and the average grain size of the martensite and the tempered martensite are determined in accordance with the instructions given in the respective parts of the description. C: 0.09% or more and 0.37% or less, Si: more than 0.70% and 2.00% or less, Mn: 2.60% or more and 3.60% or less, P: 0.001% or more and 0.100% or less, S: 0.0200% or less, Al: 0.010% or more and 1.000% or less, N: 0.0100% or less, optionally at least one selected from the group consisting of Ti: 0.001% or more and 0.100% or less, Nb: 0.001% or more and 0.100% or less, V: 0.001% or more and 0.100% or less, B: 0.0001% or more and 0.0100% or less, Mo: 0.010% or more and 0.500% or less, Cr: 0.01% or more and 1.00% or less, Cu: 0.01% or more and 1.00% or less, Ni: 0.01% or more and 0.50% or less, Sb: 0.001% or more and 0.200% or less, Sn: 0.001% or more and 0.200% or less, Ta: 0.001% or more and 0.100% or less, Ca: 0.0001% or more and 0.0200% or less, Mg: 0.0001% or more and 0.0200% or less, Zn: 0.001% or more and 0.020% or less, Co: 0.001% or more and 0.020% or less, Zr: 0.001% or more and 0.020% or less, and REM: 0.0001% or more and 0.0200% or less, with the balance being Fe and unavoidable impurities, wherein the high-strength steel sheet has a steel structure in which an area fraction of martensite having a carbon concentration of more than 0.7 × [%C] and less than 1.5 × [%C] is 55% or more; an area fraction of tempered martensite having a carbon concentration of 0.7 × [%C] or less is 5% or more and 40% or less; the ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite is 0.05 or more and 0.40 or less; and the martensite and the tempered martensite each have an average grain size of 5.3 μm or less, where [%C] represents the content in percent by mass of compositional element C in steel, wherein the area fraction of steel structures other than said martensite, tempered martensite and retained austenite is 3% or less, and wherein the tensile strength, the area fraction of martensite having a carbon concentration of more than 0.7 × [%C] and less than 1.5 × [%C], the area fraction of tempered martensite having a carbon concentration of 0.7 × [%C] or less, the ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite and the average grain size of the martensite and the tempered martensite are determined in accordance with the instructions given in the respective parts of the description.