A high-strength steel sheet having a tensile strength of 780 MPa or more, the high-strength steel sheet having a chemical composition comprising, in mass %, C: from 0.07% to 0.15% inclusive, Si: from 0.01% to 0.50% inclusive, Mn: from 1.6% to 2.4% inclusive, P: from 0.001% to 0.050% inclusive, S: from 0.0005% to 0.010% inclusive, sol. Al: from 0.005% to 0.100% inclusive, N: from 0.0001% to 0.0060% inclusive, Ti: from 0.01% to 0.10% inclusive, one or both of (i) at least one selected from Mo: from 0.05% to 1.00% inclusive, Cr: from 0.05% to 1.00% inclusive, V: from 0.02% to 0.50% inclusive, Zr: from 0.02% to 0.20% inclusive, B: from 0.0001% to 0.0030% inclusive, Cu: from 0.05% to 1.00% inclusive, and Ni: from 0.05% to 1.00% inclusive, and (ii) at least one element selected from Ca: from 0.001% to 0.005% inclusive, Sb: from 0.0030% to 0.0100% inclusive, and REM: from 0.001% to 0.005% inclusive, and optionally Nb: from 0.01% to 0.10% inclusive, with the balance being Fe and unavoidable impurities, the total content of Ti and Nb being from 0.04% to 0.17% inclusive, the chemical composition satisfying formula below, wherein the high-strength steel sheet has a steel structure containing a ferrite phase at an area fraction of from 70% to 90% inclusive, and a martensite phase at an area fraction of from 10% to 30% inclusive, wherein the rest of the steel structure may include a perlite phase, a bainite phase, a retained austenite phase, or carbides, the total area fraction of these phases in the steel structure being 3% or less, wherein the ratio of non-recrystallized ferrite contained in the ferrite phase is from 30% to 50% inclusive, wherein, in the martensite phase, the area fraction of crystal grains with an aspect ratio of from 1.0 to 1.5 inclusive is 40% to 100%, wherein the martensite phase has an average grain diameter of 2.0 μm or less, wherein the tensile strength is determined by a tensile test according to the specifications of JIS Z 2241 taking a JIS No. 5 tensile test specimen from the steel sheet and using a direction 90° with respect to the rolling direction as a tensile direction, wherein the steel structure is determined by observing a vertical cross section parallel to the rolling direction of a specimen taken from of the steel sheet, and wherein the average grain diameter of the martensite is determined by using a cutting method according to the specifications of JIS G 0522, wherein the area fractions of the phases, the average grain diameter of the martensite, the aspect ratio in the martensite phase are measured using procedures as described in the description: 0.05 ≤ C − 12 / 93 Nb − 12 / 48 Ti − 48 / 14 N − 48 / 32 S ≤ 0.10, wherein, in formula, each element symbol represents the content by mass% of the element and is 0 when the element is not contained. (i) at least one selected from Mo: from 0.05% to 1.00% inclusive, Cr: from 0.05% to 1.00% inclusive, V: from 0.02% to 0.50% inclusive, Zr: from 0.02% to 0.20% inclusive, B: from 0.0001% to 0.0030% inclusive, Cu: from 0.05% to 1.00% inclusive, and Ni: from 0.05% to 1.00% inclusive, and (ii) at least one element selected from Ca: from 0.001% to 0.005% inclusive, Sb: from 0.0030% to 0.0100% inclusive, and REM: from 0.001% to 0.005% inclusive, and optionally Nb: from 0.01% to 0.10% inclusive, with the balance being Fe and unavoidable impurities, the total content of Ti and Nb being from 0.04% to 0.17% inclusive, the chemical composition satisfying formula below, wherein the high-strength steel sheet has a steel structure containing a ferrite phase at an area fraction of from 70% to 90% inclusive, and a martensite phase at an area fraction of from 10% to 30% inclusive, wherein the rest of the steel structure may include a perlite phase, a bainite phase, a retained austenite phase, or carbides, the total area fraction of these phases in the steel structure being 3% or less, wherein the ratio of non-recrystallized ferrite contained in the ferrite phase is from 30% to 50% inclusive, wherein, in the martensite phase, the area fraction of crystal grains with an aspect ratio of from 1.0 to 1.5 inclusive is 40% to 100%, wherein the martensite phase has an average grain diameter of 2.0 μm or less, wherein the tensile strength is determined by a tensile test according to the specifications of JIS Z 2241 taking a JIS No. 5 tensile test specimen from the steel sheet and using a direction 90° with respect to the rolling direction as a tensile direction, wherein the steel structure is determined by observing a vertical cross section parallel to the rolling direction of a specimen taken from of the steel sheet, and wherein the average grain diameter of the martensite is determined by using a cutting method according to the specifications of JIS G 0522, wherein the area fractions of the phases, the average grain diameter of the martensite, the aspect ratio in the martensite phase are measured using procedures as described in the description: 0.05 ≤ C − 12 / 93 Nb − 12 / 48 Ti − 48 / 14 N − 48 / 32 S ≤ 0.10, wherein, in formula, each element symbol represents the content by mass% of the element and is 0 when the element is not contained.