A steel sheet comprising: a composition containing, in mass%, C: 0.07% or more and 0.20% or less, Si: 0.60% or more and 1.65% or less, Mn: 1.8% or more and 3.5% or less, P: 0.05% or less, S: 0.005% or less, Al: 0.08% or less, N: 0.0060% or less, optionally one or two or more selected from V: 0.001% or more and 1% or less, Ti: 0.001% or more and 0.3% or less, and Nb: 0.001% or more and 0.3% or less, optionally one or two or more selected from Cr: 0.001% or more and 1.0% or less, Mo: 0.001% or more and 1.0% or less, Ni: 0.001% or more and 1.0% or less, B: 0.0001% or more and 0.0050% or less, and Sb: 0.001% or more and 0.050% or less, optionally one or two or more selected from REM, Sn, Mg, and Ca of 0.0001% or more and 0.1% or less in total, and the balance being Fe and unavoidable impurities;a microstructure containing, by area fraction, ferrite of 30% or less and including 0%, tempered martensite of 70% or more and including 100%, and the balance other than the ferrite and the tempered martensite including 10% or less and including 0% in total, the tempered martensite having an average grain size of is 5 μm or less, the tempered martensite having iron-based carbides, which have an average particle size of 100 nm or less, precipitated on grain boundaries thereof, and the tempered martensite containing, in terms of atomic concentration, 5% or more in total of Si and Mn on the grain boundaries of the tempered martensite, wherein the atomic concentration on the grain boundaries of the tempered martensite was measured as indicated in the description; and a tensile strength of 900 MPa or higher in a direction perpendicular to the rolling direction and measured according to the provision of JIS Z 2241:2011, wherein the microstructure contains a carbide containing at least one of V, Ti, and Nb and having an average particle size of 20 nm or less if the composition contains, in mass%, one or two or more selected from V: 0.001% or more and 1% or less, Ti: 0.001% or more and 0.3% or less, and Nb: 0.001% or more and 0.3% or less and wherein the microstructure contains, in terms of atomic concentration, 5% or more in total of Cr, Mo, Ni, B, and Sb on the grain boundaries of the tempered martensite if the composition contains, in mass%, one or two or more selected from Cr: 0.001% or more and 1.0% or less, Mo: 0.001% or more and 1.0% or less, Ni: 0.001% or more and 1.0% or less, B: 0.0001% or more and 0.0050% or less, and Sb: 0.001% or more and 0.050% or less. C: 0.07% or more and 0.20% or less, Si: 0.60% or more and 1.65% or less, Mn: 1.8% or more and 3.5% or less, P: 0.05% or less, S: 0.005% or less, Al: 0.08% or less, N: 0.0060% or less, V: 0.001% or more and 1% or less, Ti: 0.001% or more and 0.3% or less, and Nb: 0.001% or more and 0.3% or less, Cr: 0.001% or more and 1.0% or less, Mo: 0.001% or more and 1.0% or less, Ni: 0.001% or more and 1.0% or less, B: 0.0001% or more and 0.0050% or less, and Sb: 0.001% or more and 0.050% or less, V: 0.001% or more and 1% or less, Ti: 0.001% or more and 0.3% or less, and Nb: 0.001% or more and 0.3% or less Cr: 0.001% or more and 1.0% or less, Mo: 0.001% or more and 1.0% or less, Ni: 0.001% or more and 1.0% or less, B: 0.0001% or more and 0.0050% or less, and Sb: 0.001% or more and 0.050% or less.