A high strength steel sheet having tensile strength of at least 1470 MPa and (tensile strength x total elongation (T. EL)) of at least 29000 MPa · %, consisting of, by mass %, C: 0.30% to 0.73% (inclusive of 0.30% and 0.73%), Si: 3.0% or less, Al: 3.0% or less, Si + Al: at least 0.7%, Cr: 0.2% to 8.0% (inclusive of 0.2% and 8.0%), Mn: 10.0% or less, Cr + Mn + Ni: at least 1.0%, P: 0.1% or less, S: 0.07% or less N: 0.010% or less, and optionally further consisting of, at least one type of elements selected from Ni: 0.05% to 5.0% (inclusive of 0.05% and 5.0%) V: 0.005% to 1.0% (inclusive of 0.005% and 1.0%), Mo: 0.005% to 0.5% (inclusive of 0.005% and 0.5%), Cu: 0.05% to 2.0% (inclusive of 0.05% and 2.0%), Ti: 0.01 % to 0.1 % (inclusive of 0.01 % and 0.1 %), Nb: 0.01 % to 0.1 % (inclusive of 0.01% and 0.1 %), B: 0.0003% to 0.0050% (inclusive of 0.0003% and 0.0050%), Ca: 0.001% to 0.005% (inclusive of 0.001% and 0.005%), REM: 0.001% to 0.005% (inclusive of 0.001% and 0.005%), and remainder as Fe and incidental impurities, wherein microstructure of the steel sheet satisfies following conditions: - area ratio of martensite with respect to the entire microstructure of the steel sheet is in the range of 15% to 90% (inclusive of 15% and 90%); - content of retained austenite is in the range of 10% to 50% (inclusive of 10% and 50%); at least 50% of said martensite is constituted of tempered martensite and area ratio of said tempered martensite with respect to the entire microstructure of the steel sheet is at least 10%; and - area ratio of polygonal ferrite with respect to the entire microstructure of the steel sheet is 10% or less (inclusive of 0%), the balance being - upper bainite in the range of 60% or less in area ratio with to the entire microstructure, - pearlite, widmanstätten ferrite and lower bainite in the range of 20% or less in total in area ratio with to the entire microstructure, and - prior austenite grain boundary, by at least 30% of the entire length thereof, exists in or is adjacent to said tempered martensite. C: 0.30% to 0.73% (inclusive of 0.30% and 0.73%), Si: 3.0% or less, Al: 3.0% or less, Si + Al: at least 0.7%, Cr: 0.2% to 8.0% (inclusive of 0.2% and 8.0%), Mn: 10.0% or less, Cr + Mn + Ni: at least 1.0%, P: 0.1% or less, S: 0.07% or less N: 0.010% or less, Ni: 0.05% to 5.0% (inclusive of 0.05% and 5.0%) V: 0.005% to 1.0% (inclusive of 0.005% and 1.0%), Mo: 0.005% to 0.5% (inclusive of 0.005% and 0.5%), Cu: 0.05% to 2.0% (inclusive of 0.05% and 2.0%), Ti: 0.01 % to 0.1 % (inclusive of 0.01 % and 0.1 %), Nb: 0.01 % to 0.1 % (inclusive of 0.01% and 0.1 %), B: 0.0003% to 0.0050% (inclusive of 0.0003% and 0.0050%), Ca: 0.001% to 0.005% (inclusive of 0.001% and 0.005%), REM: 0.001% to 0.005% (inclusive of 0.001% and 0.005%), and - area ratio of martensite with respect to the entire microstructure of the steel sheet is in the range of 15% to 90% (inclusive of 15% and 90%); - content of retained austenite is in the range of 10% to 50% (inclusive of 10% and 50%); at least 50% of said martensite is constituted of tempered martensite and area ratio of said tempered martensite with respect to the entire microstructure of the steel sheet is at least 10%; and - area ratio of polygonal ferrite with respect to the entire microstructure of the steel sheet is 10% or less (inclusive of 0%), - upper bainite in the range of 60% or less in area ratio with to the entire microstructure, - pearlite, widmanstätten ferrite and lower bainite in the range of 20% or less in total in area ratio with to the entire microstructure, and - prior austenite grain boundary, by at least 30% of the entire length thereof, exists in or is adjacent to said tempered martensite.