A hot-rolled steel sheet having a composition, consisting of, on a mass percent basis: C: 0.03% to 0.10%, Si: 0.01% to 0.50%, Mn: 1.4% to 2.2%, P: 0.001% to 0.025%, S: 0.0001% to 0.005%, Al: 0.005% to 0.10%, Nb: 0.02% to 0.10%, Ti: 0.001% to 0.030%, Mo: 0.01% to 0.50%, Cr: 0.01% to 0.50%, Ni: 0.01% to 0.50%, optionally one or two or more selected from Cu: 0.50% or less, V: 0.10% or less, and B: 0.0005% or less, optionally Ca: 0.0005% to 0.0050% by mass, and a remainder of Fe and incidental impurities, wherein incidental impurities include N: 0.005% or less, O: 0.005% or less, Mg: 0.003% or less, and/or Sn: 0.005% or less, wherein the hot-rolled steel sheet includes an inner layer having a depth of 1.5 mm or more from the front and back sides of the steel sheet in the thickness direction and having a microstructure that contains a main phase having an occupied area of 50% by area or more and a second phase, the main phase being bainitic ferrite having an average grain size of 10 μm or less, the second phase having massive martensite having an area fraction in the range of 1.4% to 15% and an aspect ratio of less than 5.0, the hot-rolled steel sheet includes an outer layer having a microstructure that contains a tempered martensite phase or a tempered martensite phase and a tempered bainite phase, wherein the area fraction of the tempered martensite phase ranges from 60% to 100% and the area fraction of the tempered bainite phase ranges from 0% to 40%, and wherein the composition has Moeq defined by the following formula in the range of 1.4% to 2.2% by mass: Moeq % = Mo + 0.36 Cr + 0.77 Mn + 0.07 Ni wherein Mn, Ni, Cr, and Mo denote the corresponding element contents in % by mass. C: 0.03% to 0.10%, Si: 0.01% to 0.50%, Mn: 1.4% to 2.2%, P: 0.001% to 0.025%, S: 0.0001% to 0.005%, Al: 0.005% to 0.10%, Nb: 0.02% to 0.10%, Ti: 0.001% to 0.030%, Mo: 0.01% to 0.50%, Cr: 0.01% to 0.50%, Ni: 0.01% to 0.50%, optionally one or two or more selected from Cu: 0.50% or less, V: 0.10% or less, and B: 0.0005% or less, optionally Ca: 0.0005% to 0.0050% by mass, and a remainder of Fe and incidental impurities, wherein incidental impurities include N: 0.005% or less, O: 0.005% or less, Mg: 0.003% or less, and/or Sn: 0.005% or less, wherein the hot-rolled steel sheet includes an inner layer having a depth of 1.5 mm or more from the front and back sides of the steel sheet in the thickness direction and having a microstructure that contains a main phase having an occupied area of 50% by area or more and a second phase, the main phase being bainitic ferrite having an average grain size of 10 μm or less, the second phase having massive martensite having an area fraction in the range of 1.4% to 15% and an aspect ratio of less than 5.0, the hot-rolled steel sheet includes an outer layer having a microstructure that contains a tempered martensite phase or a tempered martensite phase and a tempered bainite phase, wherein the area fraction of the tempered martensite phase ranges from 60% to 100% and the area fraction of the tempered bainite phase ranges from 0% to 40%, and wherein the composition has Moeq defined by the following formula in the range of 1.4% to 2.2% by mass: Moeq % = Mo + 0.36 Cr + 0.77 Mn + 0.07 Ni wherein Mn, Ni, Cr, and Mo denote the corresponding element contents in % by mass. <EOS>