This high-strength steel sheet contains, in mass %, 0.05 to 0.3% of C, 1 to 3% of Si, 0.5 to 3% of Mn, up to 0.1% (inclusive of 0%) of P, up to 0.01% (inclusive of 0%) of S, 0.001 to 0.1% of Al and 0.002 to 0.03% of N with the balance consisting of iron and unavoidable impurities, and has a microstructure which comprises, in area fraction relative to the microstructure, 40 to 85% of bainitic ferrite, 5 to 20% of retained austenite (γR), 10 to 50% (in total) of martensite and γR, and 5 to 40% of ferrite. The retained austenite (γR) has a C concentration of 0.5 to 1.0 mass %, while the quantity of γR present in the ferrite grains is 1% or more (in area fraction) relative to the microstructure.