A high strength steel sheet with 780 MPa or above tensile strength excellent in bending workability and fatigue strength, wherein a steel composition contains: C: 0.05-0.20% (in mass% with respect to chemical composition, hereinafter the same); Si: 0.6-2.0%; Mn: 1.6-3.0%; P: 0.05% or below; S: 0.01% or below; Al: 0.1% or below; N: 0.01% or below; and optionally Cu: 1.0% or below; Ni: 1.0% or below; B: 0.003% or below; V 0.3% or below; Mg: 0.001% or below; Sn, Zn, Zr, W, As, Pb, and Bi in a total quantity of 0.01% or below; at least one kind selected from a group comprising: Nb: 0.1% or below; Ti: 0.2% or below; Cr: 1.0% or below; and Mo: 0.5% or below; at least one of: Ca: 0.003% or below; and REM: 0.003% or below; and the balance iron and inevitable impurities, and a microstructure comprises a polygonal ferrite structure and a structure formed by low-temperature transformation which is at least one of martensite, tempered marteniste, bainite, and retained austenite, in which when a plane located at a depth of 0.1 mm from a surface of the steel sheet is in the observation under a scanning electron microscope with respect to twenty sights in total in different positions in the sheet-width direction, the maximum value of areal proportion of the polygonal ferrite (Fmax) and the minimum value of areal proportion of the polygonal ferrite (Fmin) in a 50 μm × 50 μm area in each sight satisfy all of Fmax≤80%, Fmin≥10%, and Fmax-Fmin≤40%. a steel composition contains: C: 0.05-0.20% (in mass% with respect to chemical composition, hereinafter the same); Si: 0.6-2.0%; Mn: 1.6-3.0%; P: 0.05% or below; S: 0.01% or below; Al: 0.1% or below; N: 0.01% or below; and optionally Cu: 1.0% or below; Ni: 1.0% or below; B: 0.003% or below; V 0.3% or below; Mg: 0.001% or below; Sn, Zn, Zr, W, As, Pb, and Bi in a total quantity of 0.01% or below; at least one kind selected from a group comprising: Nb: 0.1% or below; Ti: 0.2% or below; Cr: 1.0% or below; and Mo: 0.5% or below; at least one of: Ca: 0.003% or below; and REM: 0.003% or below; and the balance iron and inevitable impurities, and C: 0.05-0.20% (in mass% with respect to chemical composition, hereinafter the same); Si: 0.6-2.0%; Mn: 1.6-3.0%; P: 0.05% or below; S: 0.01% or below; Al: 0.1% or below; N: 0.01% or below; and optionally Cu: 1.0% or below; Ni: 1.0% or below; B: 0.003% or below; V 0.3% or below; Mg: 0.001% or below; Sn, Zn, Zr, W, As, Pb, and Bi in a total quantity of 0.01% or below; at least one kind selected from a group comprising: Nb: 0.1% or below; Ti: 0.2% or below; Cr: 1.0% or below; and Mo: 0.5% or below; Nb: 0.1% or below; Ti: 0.2% or below; Cr: 1.0% or below; and Mo: 0.5% or below; at least one of: Ca: 0.003% or below; and REM: 0.003% or below; and the balance iron and inevitable impurities, and Ca: 0.003% or below; and REM: 0.003% or below; and the balance iron and inevitable impurities, and a microstructure comprises a polygonal ferrite structure and a structure formed by low-temperature transformation which is at least one of martensite, tempered marteniste, bainite, and retained austenite, in which when a plane located at a depth of 0.1 mm from a surface of the steel sheet is in the observation under a scanning electron microscope with respect to twenty sights in total in different positions in the sheet-width direction, the maximum value of areal proportion of the polygonal ferrite (Fmax) and the minimum value of areal proportion of the polygonal ferrite (Fmin) in a 50 μm × 50 μm area in each sight satisfy all of Fmax≤80%, Fmin≥10%, and Fmax-Fmin≤40%.