A high-strength steel sheet comprising: a component composition containing, on a percent by mass basis: C: 0.15% to 0.40%, Si: 0.5% to 2.5%, Mn: 1.0% to 2.0%, P: 0.1% or lower, S: 0.01% or lower, Al: 0.01% to 0.5%, and N: 0.010% or lower, optionally one or more selected from Cr: 0.005% to 1.0%, V: 0.005% to 1.0%, Ni: 0.005% to 1.0%, Mo: 0.005% to 1.0%, Cu: 0.01% to 2.0%, Ti: 0.005% to 0.1%, Nb: 0.005% to 0.1%, B: 0.0003% to 0.0050%, Ca: 0.001% to 0.005% and REM: 0.001% to 0.005%, the balance being substantially Fe and incidental impurities; and a steel microstructure containing, on an area-percentage basis with respect to the entire steel microstructure, 40% or more and less than 85% of a lower bainite, 10% or more and less than 40% martensite including tempered martensite, 10% or more and 30% or less retained austenite, and 10% or less (including 0%) polygonal ferrite, the retained austenite having an average C content of 0.60% by mass or more, wherein a Mn segregation value defined by a difference between maximum and minimum values of a Mn concentration at a surface measured with an EPMA is 0.8% or less, a tensile strength is 1,320 MPa or more, a ratio R/t of a limit bending radius (R) to a thickness (t) is 2.0 or less, tensile strength × total elongation is 15,000 MPa·% or more, and tensile strength × hole expansion ratio is 50,000 MPa·% or more, and the limit bending radius is measured according to JIS Z2248, the tensile strength and the total elongation are measured according to JISZ2241, and the hole expansion ratio is measured according to JFST 1001. a component composition containing, on a percent by mass basis: C: 0.15% to 0.40%, Si: 0.5% to 2.5%, Mn: 1.0% to 2.0%, P: 0.1% or lower, S: 0.01% or lower, Al: 0.01% to 0.5%, and N: 0.010% or lower, optionally one or more selected from Cr: 0.005% to 1.0%, V: 0.005% to 1.0%, Ni: 0.005% to 1.0%, Mo: 0.005% to 1.0%, Cu: 0.01% to 2.0%, Ti: 0.005% to 0.1%, Nb: 0.005% to 0.1%, B: 0.0003% to 0.0050%, Ca: 0.001% to 0.005% and REM: 0.001% to 0.005%, the balance being substantially Fe and incidental impurities; and C: 0.15% to 0.40%, Si: 0.5% to 2.5%, Mn: 1.0% to 2.0%, P: 0.1% or lower, S: 0.01% or lower, Al: 0.01% to 0.5%, and N: 0.010% or lower, optionally one or more selected from Cr: 0.005% to 1.0%, V: 0.005% to 1.0%, Ni: 0.005% to 1.0%, Mo: 0.005% to 1.0%, Cu: 0.01% to 2.0%, Ti: 0.005% to 0.1%, Nb: 0.005% to 0.1%, B: 0.0003% to 0.0050%, Ca: 0.001% to 0.005% and REM: 0.001% to 0.005%, the balance being substantially Fe and incidental impurities; and a steel microstructure containing, on an area-percentage basis with respect to the entire steel microstructure, 40% or more and less than 85% of a lower bainite, 10% or more and less than 40% martensite including tempered martensite, 10% or more and 30% or less retained austenite, and 10% or less (including 0%) polygonal ferrite, the retained austenite having an average C content of 0.60% by mass or more, wherein a Mn segregation value defined by a difference between maximum and minimum values of a Mn concentration at a surface measured with an EPMA is 0.8% or less, a tensile strength is 1,320 MPa or more, a ratio R/t of a limit bending radius (R) to a thickness (t) is 2.0 or less, tensile strength × total elongation is 15,000 MPa·% or more, and tensile strength × hole expansion ratio is 50,000 MPa·% or more, and the limit bending radius is measured according to JIS Z2248, the tensile strength and the total elongation are measured according to JISZ2241, and the hole expansion ratio is measured according to JFST 1001. <EOS>